def test_hyperexpand_bases():
assert (hyperexpand(hyper([2], [a], z)) == a + z**(-a + 1) *
(-(a**2) + 3 * a + z *
(a - 1) - 2) * exp(z) * lowergamma(a - 1, z) - 1)
# TODO [a+1, aRational(-1, 2)], [2*a]
assert hyperexpand(hyper([1, 2], [3],
z)) == -2 / z - 2 * log(-z + 1) / z**2
assert (hyperexpand(hyper([S.Half, 2], [Rational(3, 2)], z)) == -1 /
(2 * z - 2) + atanh(sqrt(z)) / sqrt(z) / 2)
assert hyperexpand(hyper(
[S.Half, S.Half], [Rational(5, 2)],
z)) == (-3 * z + 3) / 4 / (z * sqrt(-z + 1)) + (6 * z - 3) * asin(
sqrt(z)) / (4 * z**Rational(3, 2))
assert hyperexpand(hyper(
[1, 2], [Rational(3, 2)],
z)) == -1 / (2 * z - 2) - asin(sqrt(z)) / (sqrt(z) *
(2 * z - 2) * sqrt(-z + 1))
assert hyperexpand(
hyper([Rational(-1, 2) - 1, 1, 2], [S.Half, 3],
z)) == sqrt(z) * (z * Rational(6, 7) - Rational(6, 5)) * atanh(
sqrt(z)) + (-30 * z**2 + 32 * z -
6) / 35 / z - 6 * log(-z + 1) / (35 * z**2)
assert (hyperexpand(hyper([1 + S.Half, 1, 1], [2, 2],
z)) == -4 * log(sqrt(-z + 1) / 2 + S.Half) / z)
# TODO hyperexpand(hyper([a], [2*a + 1], z))
# TODO [S.Half, a], [Rational(3, 2), a+1]
assert hyperexpand(hyper(
[2], [b, 1],
z)) == z**(-b / 2 + S.Half) * besseli(b - 1, 2 * sqrt(z)) * gamma(
b) + z**(-b / 2 + 1) * besseli(b, 2 * sqrt(z)) * gamma(b)
def test_airybiprime():
z = Symbol('z', real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airybiprime(z), airybiprime)
assert airybiprime(0) == 3**(S(1)/6)/gamma(S(1)/3)
assert airybiprime(oo) == oo
assert airybiprime(-oo) == 0
assert diff(airybiprime(z), z) == z*airybi(z)
assert series(airybiprime(z), z, 0, 3) == (
3**(S(1)/6)/gamma(S(1)/3) + 3**(S(5)/6)*z**2/(6*gamma(S(2)/3)) + O(z**3))
assert airybiprime(z).rewrite(hyper) == (
3**(S(5)/6)*z**2*hyper((), (S(5)/3,), z**S(3)/9)/(6*gamma(S(2)/3)) +
3**(S(1)/6)*hyper((), (S(1)/3,), z**S(3)/9)/gamma(S(1)/3))
assert isinstance(airybiprime(z).rewrite(besselj), airybiprime)
assert airyai(t).rewrite(besselj) == (
sqrt(-t)*(besselj(-S(1)/3, 2*(-t)**(S(3)/2)/3) +
besselj(S(1)/3, 2*(-t)**(S(3)/2)/3))/3)
assert airybiprime(z).rewrite(besseli) == (
sqrt(3)*(z**2*besseli(S(2)/3, 2*z**(S(3)/2)/3)/(z**(S(3)/2))**(S(2)/3) +
(z**(S(3)/2))**(S(2)/3)*besseli(-S(2)/3, 2*z**(S(3)/2)/3))/3)
assert airybiprime(p).rewrite(besseli) == (
sqrt(3)*p*(besseli(-S(2)/3, 2*p**(S(3)/2)/3) + besseli(S(2)/3, 2*p**(S(3)/2)/3))/3)
assert expand_func(airybiprime(2*(3*z**5)**(S(1)/3))) == (
sqrt(3)*(z**(S(5)/3)/(z**5)**(S(1)/3) - 1)*airyaiprime(2*3**(S(1)/3)*z**(S(5)/3))/2 +
(z**(S(5)/3)/(z**5)**(S(1)/3) + 1)*airybiprime(2*3**(S(1)/3)*z**(S(5)/3))/2)
def test_airyaiprime():
z = Symbol('z', real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airyaiprime(z), airyaiprime)
assert airyaiprime(0) == -3**(S(2)/3)/(3*gamma(S(1)/3))
assert airyaiprime(oo) == 0
assert diff(airyaiprime(z), z) == z*airyai(z)
assert series(airyaiprime(z), z, 0, 3) == (
-3**(S(2)/3)/(3*gamma(S(1)/3)) + 3**(S(1)/3)*z**2/(6*gamma(S(2)/3)) + O(z**3))
assert airyaiprime(z).rewrite(hyper) == (
3**(S(1)/3)*z**2*hyper((), (S(5)/3,), z**S(3)/9)/(6*gamma(S(2)/3)) -
3**(S(2)/3)*hyper((), (S(1)/3,), z**S(3)/9)/(3*gamma(S(1)/3)))
assert isinstance(airyaiprime(z).rewrite(besselj), airyaiprime)
assert airyai(t).rewrite(besselj) == (
sqrt(-t)*(besselj(-S(1)/3, 2*(-t)**(S(3)/2)/3) +
besselj(S(1)/3, 2*(-t)**(S(3)/2)/3))/3)
assert airyaiprime(z).rewrite(besseli) == (
z**2*besseli(S(2)/3, 2*z**(S(3)/2)/3)/(3*(z**(S(3)/2))**(S(2)/3)) -
(z**(S(3)/2))**(S(2)/3)*besseli(-S(1)/3, 2*z**(S(3)/2)/3)/3)
assert airyaiprime(p).rewrite(besseli) == (
p*(-besseli(-S(2)/3, 2*p**(S(3)/2)/3) + besseli(S(2)/3, 2*p**(S(3)/2)/3))/3)
assert expand_func(airyaiprime(2*(3*z**5)**(S(1)/3))) == (
sqrt(3)*(z**(S(5)/3)/(z**5)**(S(1)/3) - 1)*airybiprime(2*3**(S(1)/3)*z**(S(5)/3))/6 +
(z**(S(5)/3)/(z**5)**(S(1)/3) + 1)*airyaiprime(2*3**(S(1)/3)*z**(S(5)/3))/2)
def test_airybiprime():
z = Symbol('z', real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airybiprime(z), airybiprime)
assert airybiprime(0) == 3**Rational(1, 6)/gamma(Rational(1, 3))
assert airybiprime(oo) is oo
assert airybiprime(-oo) == 0
assert diff(airybiprime(z), z) == z*airybi(z)
assert series(airybiprime(z), z, 0, 3) == (
3**Rational(1, 6)/gamma(Rational(1, 3)) + 3**Rational(5, 6)*z**2/(6*gamma(Rational(2, 3))) + O(z**3))
assert airybiprime(z).rewrite(hyper) == (
3**Rational(5, 6)*z**2*hyper((), (Rational(5, 3),), z**3/9)/(6*gamma(Rational(2, 3))) +
3**Rational(1, 6)*hyper((), (Rational(1, 3),), z**3/9)/gamma(Rational(1, 3)))
assert isinstance(airybiprime(z).rewrite(besselj), airybiprime)
assert airyai(t).rewrite(besselj) == (
sqrt(-t)*(besselj(Rational(-1, 3), 2*(-t)**Rational(3, 2)/3) +
besselj(Rational(1, 3), 2*(-t)**Rational(3, 2)/3))/3)
assert airybiprime(z).rewrite(besseli) == (
sqrt(3)*(z**2*besseli(Rational(2, 3), 2*z**Rational(3, 2)/3)/(z**Rational(3, 2))**Rational(2, 3) +
(z**Rational(3, 2))**Rational(2, 3)*besseli(Rational(-2, 3), 2*z**Rational(3, 2)/3))/3)
assert airybiprime(p).rewrite(besseli) == (
sqrt(3)*p*(besseli(Rational(-2, 3), 2*p**Rational(3, 2)/3) + besseli(Rational(2, 3), 2*p**Rational(3, 2)/3))/3)
assert expand_func(airybiprime(2*(3*z**5)**Rational(1, 3))) == (
sqrt(3)*(z**Rational(5, 3)/(z**5)**Rational(1, 3) - 1)*airyaiprime(2*3**Rational(1, 3)*z**Rational(5, 3))/2 +
(z**Rational(5, 3)/(z**5)**Rational(1, 3) + 1)*airybiprime(2*3**Rational(1, 3)*z**Rational(5, 3))/2)
def test_hyperexpand_bases():
assert (
hyperexpand(hyper([2], [a], z))
== a + z ** (-a + 1) * (-a ** 2 + 3 * a + z * (a - 1) - 2) * exp(z) * lowergamma(a - 1, z) - 1
)
# TODO [a+1, a-S.Half], [2*a]
assert hyperexpand(hyper([1, 2], [3], z)) == -2 / z - 2 * log(exp_polar(-I * pi) * z + 1) / z ** 2
assert hyperexpand(hyper([S.Half, 2], [S(3) / 2], z)) == -1 / (2 * z - 2) + log((sqrt(z) + 1) / (-sqrt(z) + 1)) / (
4 * sqrt(z)
)
assert hyperexpand(hyper([S(1) / 2, S(1) / 2], [S(5) / 2], z)) == (-3 * z + 3) / 4 / (z * sqrt(-z + 1)) + (
6 * z - 3
) * asin(sqrt(z)) / (4 * z ** (S(3) / 2))
assert hyperexpand(hyper([1, 2], [S(3) / 2], z)) == -1 / (2 * z - 2) - asin(sqrt(z)) / (
sqrt(z) * (2 * z - 2) * sqrt(-z + 1)
)
assert hyperexpand(hyper([-S.Half - 1, 1, 2], [S.Half, 3], z)) == sqrt(z) * (6 * z / 7 - S(6) / 5) * atanh(
sqrt(z)
) + (-30 * z ** 2 + 32 * z - 6) / 35 / z - 6 * log(-z + 1) / (35 * z ** 2)
assert hyperexpand(hyper([1 + S.Half, 1, 1], [2, 2], z)) == -4 * log(sqrt(-z + 1) / 2 + S(1) / 2) / z
# TODO hyperexpand(hyper([a], [2*a + 1], z))
# TODO [S.Half, a], [S(3)/2, a+1]
assert hyperexpand(hyper([2], [b, 1], z)) == z ** (-b / 2 + S(1) / 2) * besseli(b - 1, 2 * sqrt(z)) * gamma(
b
) + z ** (-b / 2 + 1) * besseli(b, 2 * sqrt(z)) * gamma(b)
def test_airyai():
z = Symbol('z', real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airyai(z), airyai)
assert airyai(0) == 3**(S(1)/3)/(3*gamma(S(2)/3))
assert airyai(oo) == 0
assert airyai(-oo) == 0
assert diff(airyai(z), z) == airyaiprime(z)
assert series(airyai(z), z, 0, 3) == (
3**(S(5)/6)*gamma(S(1)/3)/(6*pi) - 3**(S(1)/6)*z*gamma(S(2)/3)/(2*pi) + O(z**3))
assert airyai(z).rewrite(hyper) == (
-3**(S(2)/3)*z*hyper((), (S(4)/3,), z**S(3)/9)/(3*gamma(S(1)/3)) +
3**(S(1)/3)*hyper((), (S(2)/3,), z**S(3)/9)/(3*gamma(S(2)/3)))
assert isinstance(airyai(z).rewrite(besselj), airyai)
assert airyai(t).rewrite(besselj) == (
sqrt(-t)*(besselj(-S(1)/3, 2*(-t)**(S(3)/2)/3) +
besselj(S(1)/3, 2*(-t)**(S(3)/2)/3))/3)
assert airyai(z).rewrite(besseli) == (
-z*besseli(S(1)/3, 2*z**(S(3)/2)/3)/(3*(z**(S(3)/2))**(S(1)/3)) +
(z**(S(3)/2))**(S(1)/3)*besseli(-S(1)/3, 2*z**(S(3)/2)/3)/3)
assert airyai(p).rewrite(besseli) == (
sqrt(p)*(besseli(-S(1)/3, 2*p**(S(3)/2)/3) -
besseli(S(1)/3, 2*p**(S(3)/2)/3))/3)
assert expand_func(airyai(2*(3*z**5)**(S(1)/3))) == (
-sqrt(3)*(-1 + (z**5)**(S(1)/3)/z**(S(5)/3))*airybi(2*3**(S(1)/3)*z**(S(5)/3))/6 +
(1 + (z**5)**(S(1)/3)/z**(S(5)/3))*airyai(2*3**(S(1)/3)*z**(S(5)/3))/2)
def test_diff():
assert besselj(n, z).diff(z) == besselj(n - 1, z)/2 - besselj(n + 1, z)/2
assert bessely(n, z).diff(z) == bessely(n - 1, z)/2 - bessely(n + 1, z)/2
assert besseli(n, z).diff(z) == besseli(n - 1, z)/2 + besseli(n + 1, z)/2
assert besselk(n, z).diff(z) == -besselk(n - 1, z)/2 - besselk(n + 1, z)/2
assert hankel1(n, z).diff(z) == hankel1(n - 1, z)/2 - hankel1(n + 1, z)/2
assert hankel2(n, z).diff(z) == hankel2(n - 1, z)/2 - hankel2(n + 1, z)/2
def test_airybi():
z = Symbol('z', real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airybi(z), airybi)
assert airybi(0) == 3**(S(5)/6)/(3*gamma(S(2)/3))
assert airybi(oo) == oo
assert airybi(-oo) == 0
assert diff(airybi(z), z) == airybiprime(z)
assert series(airybi(z), z, 0, 3) == (
3**(S(1)/3)*gamma(S(1)/3)/(2*pi) + 3**(S(2)/3)*z*gamma(S(2)/3)/(2*pi) + O(z**3))
assert airybi(z).rewrite(hyper) == (
3**(S(1)/6)*z*hyper((), (S(4)/3,), z**S(3)/9)/gamma(S(1)/3) +
3**(S(5)/6)*hyper((), (S(2)/3,), z**S(3)/9)/(3*gamma(S(2)/3)))
assert isinstance(airybi(z).rewrite(besselj), airybi)
assert airyai(t).rewrite(besselj) == (
sqrt(-t)*(besselj(-S(1)/3, 2*(-t)**(S(3)/2)/3) +
besselj(S(1)/3, 2*(-t)**(S(3)/2)/3))/3)
assert airybi(z).rewrite(besseli) == (
sqrt(3)*(z*besseli(S(1)/3, 2*z**(S(3)/2)/3)/(z**(S(3)/2))**(S(1)/3) +
(z**(S(3)/2))**(S(1)/3)*besseli(-S(1)/3, 2*z**(S(3)/2)/3))/3)
assert airybi(p).rewrite(besseli) == (
sqrt(3)*sqrt(p)*(besseli(-S(1)/3, 2*p**(S(3)/2)/3) +
besseli(S(1)/3, 2*p**(S(3)/2)/3))/3)
assert expand_func(airybi(2*(3*z**5)**(S(1)/3))) == (
sqrt(3)*(1 - (z**5)**(S(1)/3)/z**(S(5)/3))*airyai(2*3**(S(1)/3)*z**(S(5)/3))/2 +
(1 + (z**5)**(S(1)/3)/z**(S(5)/3))*airybi(2*3**(S(1)/3)*z**(S(5)/3))/2)
def test_diff():
assert besselj(n, z).diff(z) == besselj(n - 1, z)/2 - besselj(n + 1, z)/2
assert bessely(n, z).diff(z) == bessely(n - 1, z)/2 - bessely(n + 1, z)/2
assert besseli(n, z).diff(z) == besseli(n - 1, z)/2 + besseli(n + 1, z)/2
assert besselk(n, z).diff(z) == -besselk(n - 1, z)/2 - besselk(n + 1, z)/2
assert hankel1(n, z).diff(z) == hankel1(n - 1, z)/2 - hankel1(n + 1, z)/2
assert hankel2(n, z).diff(z) == hankel2(n - 1, z)/2 - hankel2(n + 1, z)/2
def test_airyai():
z = Symbol('z', real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airyai(z), airyai)
assert airyai(0) == 3**Rational(1, 3)/(3*gamma(Rational(2, 3)))
assert airyai(oo) == 0
assert airyai(-oo) == 0
assert diff(airyai(z), z) == airyaiprime(z)
assert series(airyai(z), z, 0, 3) == (
3**Rational(5, 6)*gamma(Rational(1, 3))/(6*pi) - 3**Rational(1, 6)*z*gamma(Rational(2, 3))/(2*pi) + O(z**3))
assert airyai(z).rewrite(hyper) == (
-3**Rational(2, 3)*z*hyper((), (Rational(4, 3),), z**3/9)/(3*gamma(Rational(1, 3))) +
3**Rational(1, 3)*hyper((), (Rational(2, 3),), z**3/9)/(3*gamma(Rational(2, 3))))
assert isinstance(airyai(z).rewrite(besselj), airyai)
assert airyai(t).rewrite(besselj) == (
sqrt(-t)*(besselj(Rational(-1, 3), 2*(-t)**Rational(3, 2)/3) +
besselj(Rational(1, 3), 2*(-t)**Rational(3, 2)/3))/3)
assert airyai(z).rewrite(besseli) == (
-z*besseli(Rational(1, 3), 2*z**Rational(3, 2)/3)/(3*(z**Rational(3, 2))**Rational(1, 3)) +
(z**Rational(3, 2))**Rational(1, 3)*besseli(Rational(-1, 3), 2*z**Rational(3, 2)/3)/3)
assert airyai(p).rewrite(besseli) == (
sqrt(p)*(besseli(Rational(-1, 3), 2*p**Rational(3, 2)/3) -
besseli(Rational(1, 3), 2*p**Rational(3, 2)/3))/3)
assert expand_func(airyai(2*(3*z**5)**Rational(1, 3))) == (
-sqrt(3)*(-1 + (z**5)**Rational(1, 3)/z**Rational(5, 3))*airybi(2*3**Rational(1, 3)*z**Rational(5, 3))/6 +
(1 + (z**5)**Rational(1, 3)/z**Rational(5, 3))*airyai(2*3**Rational(1, 3)*z**Rational(5, 3))/2)
def test_rewrite():
from sympy import polar_lift, exp, I
assert besselj(n, z).rewrite(jn) == sqrt(2*z/pi)*jn(n - S(1)/2, z)
assert bessely(n, z).rewrite(yn) == sqrt(2*z/pi)*yn(n - S(1)/2, z)
assert besseli(n, z).rewrite(besselj) == \
exp(-I*n*pi/2)*besselj(n, polar_lift(I)*z)
assert besselj(n, z).rewrite(besseli) == \
exp(I*n*pi/2)*besseli(n, polar_lift(-I)*z)
nu = randcplx()
assert tn(besselj(nu, z), besselj(nu, z).rewrite(besseli), z)
assert tn(besseli(nu, z), besseli(nu, z).rewrite(besselj), z)
def test_rewrite():
from sympy import polar_lift, exp, I
assert besselj(n, z).rewrite(jn) == sqrt(2 * z / pi) * jn(n - S(1) / 2, z)
assert bessely(n, z).rewrite(yn) == sqrt(2 * z / pi) * yn(n - S(1) / 2, z)
assert besseli(n, z).rewrite(besselj) == \
exp(-I*n*pi/2)*besselj(n, polar_lift(I)*z)
assert besselj(n, z).rewrite(besseli) == \
exp(I*n*pi/2)*besseli(n, polar_lift(-I)*z)
nu = randcplx()
assert tn(besselj(nu, z), besselj(nu, z).rewrite(besseli), z)
assert tn(besseli(nu, z), besseli(nu, z).rewrite(besselj), z)
def test_find_transform(self):
cases = [(2 * pi / 3, pi), (1 / zeta(3), zeta(3)),
((8 * e + 21) / (7 - 5 * e), e),
(25 + besseli(1, 2), besseli(1, 2))]
with mpmath.workdps(100):
for t in cases:
with self.subTest(find_transform=sympy.pretty(t[0])):
y_value = lambdify((), t[0], modules="mpmath")()
x_value = lambdify((), t[1], modules="mpmath")()
transformation = find_transform(x_value, y_value, 30)
sym_transform = transformation.sym_expression(t[1])
self.assertEqual(sym_transform, t[0])
def test_bessel():
from sympy import besselj, Heaviside, besseli, polar_lift, exp_polar
assert integrate(besselj(a, z)*besselj(b, z)/z, (z, 0, oo),
meijerg=True, conds='none') == \
2*sin(pi*a/2 - pi*b/2)/(pi*(a-b)*(a+b))
assert integrate(besselj(a, z) * besselj(a, z) / z, (z, 0, oo),
meijerg=True,
conds='none') == 1 / (2 * a)
# TODO more orthogonality integrals
# TODO there is actually a lot to improve here, this example is a good
# stress-test
# (the original integral is not recognised, the convergence conditions are
# wrong, and the result can be simplified to besselj(y, z))
assert simplify(integrate(sin(z*x)*(x**2-1)**(-(y+S(1)/2))*Heaviside(x**2-1),
(x, 0, oo), meijerg=True, conds='none')
*2/((z/2)**y*sqrt(pi)*gamma(S(1)/2-y))) == \
2*(z**2/4)**(y + S(1)/2)*(z/2)**(-y)*(2*exp_polar(-I*pi/2)/z)**y \
*besseli(y, z*exp_polar(I*pi/2))/z
# Werner Rosenheinrich
# SOME INDEFINITE INTEGRALS OF BESSEL FUNCTIONS
assert integrate(x * besselj(0, x), x, meijerg=True) == x * besselj(1, x)
assert integrate(x * besseli(0, x), x, meijerg=True) == x * besseli(1, x)
# TODO can do higher powers, but come out as high order ... should they be
# reduced to order 0, 1?
assert integrate(besselj(1, x), x, meijerg=True) == -besselj(0, x)
assert integrate(besselj(1, x)**2/x, x, meijerg=True) == \
-(besselj(0, x)**2 + besselj(1, x)**2)/2
# TODO more besseli when tables are extended or recursive mellin works
assert integrate(besselj(0, x)**2/x**2, x, meijerg=True) == \
-2*x*besselj(0, x)**2 - 2*x*besselj(1, x)**2 \
+ 2*besselj(0, x)*besselj(1, x) - besselj(0, x)**2/x
assert integrate(besselj(0, x)*besselj(1, x), x, meijerg=True) == \
-besselj(0, x)**2/2
assert integrate(x**2*besselj(0, x)*besselj(1, x), x, meijerg=True) == \
x**2*besselj(1, x)**2/2
assert integrate(besselj(0, x)*besselj(1, x)/x, x, meijerg=True) == \
x*besselj(0, x)**2 + x*besselj(1, x)**2 - besselj(0, x)*besselj(1, x)
# TODO how does besselj(0, a*x)*besselj(0, b*x) work?
# TODO how does besselj(0, x)**2*besselj(1, x)**2 work?
# TODO sin(x)*besselj(0, x) etc come out a mess
# TODO can x*log(x)*besselj(0, x) be done?
# TODO how does besselj(1, x)*besselj(0, x+a) work?
# TODO more indefinite integrals when struve functions etc are implemented
# test a substitution
assert integrate(besselj(1, x**2) * x, x,
meijerg=True) == -besselj(0, x**2) / 2
def test_branching():
assert besselj(polar_lift(k), x) == besselj(k, x)
assert besseli(polar_lift(k), x) == besseli(k, x)
n = Symbol('n', integer=True)
assert besselj(n, exp_polar(2 * pi * I) * x) == besselj(n, x)
assert besselj(n, polar_lift(x)) == besselj(n, x)
assert besseli(n, exp_polar(2 * pi * I) * x) == besseli(n, x)
assert besseli(n, polar_lift(x)) == besseli(n, x)
def tn(func, s):
from random import uniform
c = uniform(1, 5)
expr = func(s, c * exp_polar(I * pi)) - func(s, c * exp_polar(-I * pi))
eps = 1e-15
expr2 = func(s + eps, -c + eps * I) - func(s + eps, -c - eps * I)
return abs(expr.n() - expr2.n()).n() < 1e-10
nu = Symbol('nu')
assert besselj(nu,
exp_polar(2 * pi * I) *
x) == exp(2 * pi * I * nu) * besselj(nu, x)
assert besseli(nu,
exp_polar(2 * pi * I) *
x) == exp(2 * pi * I * nu) * besseli(nu, x)
assert tn(besselj, 2)
assert tn(besselj, pi)
assert tn(besselj, I)
assert tn(besseli, 2)
assert tn(besseli, pi)
assert tn(besseli, I)
def test_bessel_eval():
from sympy import I
assert besselj(-4, z) == besselj(4, z)
assert besselj(-3, z) == -besselj(3, z)
assert bessely(-2, z) == bessely(2, z)
assert bessely(-1, z) == -bessely(1, z)
assert besselj(0, -z) == besselj(0, z)
assert besselj(1, -z) == -besselj(1, z)
assert besseli(0, I*z) == besselj(0, z)
assert besseli(1, I*z) == I*besselj(1, z)
assert besselj(3, I*z) == -I*besseli(3, z)
def test_bessel():
from sympy import (besselj, Heaviside, besseli, polar_lift, exp_polar,
powdenest)
assert simplify(integrate(besselj(a, z)*besselj(b, z)/z, (z, 0, oo),
meijerg=True, conds='none')) == \
2*sin(pi*a/2 - pi*b/2)/(pi*(a - b)*(a + b))
assert simplify(integrate(besselj(a, z)*besselj(a, z)/z, (z, 0, oo),
meijerg=True, conds='none')) == 1/(2*a)
# TODO more orthogonality integrals
# TODO there is some improvement possible here:
# - the result can be simplified to besselj(y, z))
assert powdenest(simplify(integrate(sin(z*x)*(x**2-1)**(-(y+S(1)/2)),
(x, 1, oo), meijerg=True, conds='none')
*2/((z/2)**y*sqrt(pi)*gamma(S(1)/2-y))),
polar=True) == \
exp(-I*pi*y/2)*besseli(y, z*exp_polar(I*pi/2))
# Werner Rosenheinrich
# SOME INDEFINITE INTEGRALS OF BESSEL FUNCTIONS
assert integrate(x*besselj(0, x), x, meijerg=True) == x*besselj(1, x)
assert integrate(x*besseli(0, x), x, meijerg=True) == x*besseli(1, x)
# TODO can do higher powers, but come out as high order ... should they be
# reduced to order 0, 1?
assert integrate(besselj(1, x), x, meijerg=True) == -besselj(0, x)
assert integrate(besselj(1, x)**2/x, x, meijerg=True) == \
-(besselj(0, x)**2 + besselj(1, x)**2)/2
# TODO more besseli when tables are extended or recursive mellin works
assert integrate(besselj(0, x)**2/x**2, x, meijerg=True) == \
-2*x*besselj(0, x)**2 - 2*x*besselj(1, x)**2 \
+ 2*besselj(0, x)*besselj(1, x) - besselj(0, x)**2/x
assert integrate(besselj(0, x)*besselj(1, x), x, meijerg=True) == \
-besselj(0, x)**2/2
assert integrate(x**2*besselj(0, x)*besselj(1, x), x, meijerg=True) == \
x**2*besselj(1, x)**2/2
assert integrate(besselj(0, x)*besselj(1, x)/x, x, meijerg=True) == \
(x*besselj(0, x)**2 + x*besselj(1, x)**2 - \
besselj(0, x)*besselj(1, x))
# TODO how does besselj(0, a*x)*besselj(0, b*x) work?
# TODO how does besselj(0, x)**2*besselj(1, x)**2 work?
# TODO sin(x)*besselj(0, x) etc come out a mess
# TODO can x*log(x)*besselj(0, x) be done?
# TODO how does besselj(1, x)*besselj(0, x+a) work?
# TODO more indefinite integrals when struve functions etc are implemented
# test a substitution
assert integrate(besselj(1, x**2)*x, x, meijerg=True) == \
-besselj(0, x**2)/2
def test_bessel_eval():
from sympy import I
assert besselj(-4, z) == besselj(4, z)
assert besselj(-3, z) == -besselj(3, z)
assert bessely(-2, z) == bessely(2, z)
assert bessely(-1, z) == -bessely(1, z)
assert besselj(0, -z) == besselj(0, z)
assert besselj(1, -z) == -besselj(1, z)
assert besseli(0, I * z) == besselj(0, z)
assert besseli(1, I * z) == I * besselj(1, z)
assert besselj(3, I * z) == -I * besseli(3, z)
def test_branching():
from sympy import exp_polar, polar_lift, Symbol, I, exp
assert besselj(polar_lift(k), x) == besselj(k, x)
assert besseli(polar_lift(k), x) == besseli(k, x)
n = Symbol('n', integer=True)
assert besselj(n, exp_polar(2*pi*I)*x) == besselj(n, x)
assert besselj(n, polar_lift(x)) == besselj(n, x)
assert besseli(n, exp_polar(2*pi*I)*x) == besseli(n, x)
assert besseli(n, polar_lift(x)) == besseli(n, x)
def tn(func, s):
from random import uniform
c = uniform(1, 5)
expr = func(s, c*exp_polar(I*pi)) - func(s, c*exp_polar(-I*pi))
eps = 1e-15
expr2 = func(s + eps, -c + eps*I) - func(s + eps, -c - eps*I)
return abs(expr.n() - expr2.n()).n() < 1e-10
nu = Symbol('nu')
assert besselj(nu, exp_polar(2*pi*I)*x) == exp(2*pi*I*nu)*besselj(nu, x)
assert besseli(nu, exp_polar(2*pi*I)*x) == exp(2*pi*I*nu)*besseli(nu, x)
assert tn(besselj, 2)
assert tn(besselj, pi)
assert tn(besselj, I)
assert tn(besseli, 2)
assert tn(besseli, pi)
assert tn(besseli, I)
def test_bessel():
from sympy import (besselj, Heaviside, besseli, polar_lift, exp_polar,
powdenest)
assert simplify(integrate(besselj(a, z)*besselj(b, z)/z, (z, 0, oo),
meijerg=True, conds='none')) == \
2*sin(pi*a/2 - pi*b/2)/(pi*(a - b)*(a + b))
assert simplify(integrate(besselj(a, z)*besselj(a, z)/z, (z, 0, oo),
meijerg=True, conds='none')) == 1/(2*a)
# TODO more orthogonality integrals
# TODO there is some improvement possible here:
# - the result can be simplified to besselj(y, z))
assert powdenest(simplify(integrate(sin(z*x)*(x**2-1)**(-(y+S(1)/2)),
(x, 1, oo), meijerg=True, conds='none')
*2/((z/2)**y*sqrt(pi)*gamma(S(1)/2-y))),
polar=True) == \
exp(-I*pi*y/2)*besseli(y, z*exp_polar(I*pi/2))
# Werner Rosenheinrich
# SOME INDEFINITE INTEGRALS OF BESSEL FUNCTIONS
assert integrate(x*besselj(0, x), x, meijerg=True) == x*besselj(1, x)
assert integrate(x*besseli(0, x), x, meijerg=True) == x*besseli(1, x)
# TODO can do higher powers, but come out as high order ... should they be
# reduced to order 0, 1?
assert integrate(besselj(1, x), x, meijerg=True) == -besselj(0, x)
assert integrate(besselj(1, x)**2/x, x, meijerg=True) == \
-(besselj(0, x)**2 + besselj(1, x)**2)/2
# TODO more besseli when tables are extended or recursive mellin works
assert integrate(besselj(0, x)**2/x**2, x, meijerg=True) == \
-2*x*besselj(0, x)**2 - 2*x*besselj(1, x)**2 \
+ 2*besselj(0, x)*besselj(1, x) - besselj(0, x)**2/x
assert integrate(besselj(0, x)*besselj(1, x), x, meijerg=True) == \
-besselj(0, x)**2/2
assert integrate(x**2*besselj(0, x)*besselj(1, x), x, meijerg=True) == \
x**2*besselj(1, x)**2/2
assert integrate(besselj(0, x)*besselj(1, x)/x, x, meijerg=True) == \
(x*besselj(0, x)**2 + x*besselj(1, x)**2 - \
besselj(0, x)*besselj(1, x))
# TODO how does besselj(0, a*x)*besselj(0, b*x) work?
# TODO how does besselj(0, x)**2*besselj(1, x)**2 work?
# TODO sin(x)*besselj(0, x) etc come out a mess
# TODO can x*log(x)*besselj(0, x) be done?
# TODO how does besselj(1, x)*besselj(0, x+a) work?
# TODO more indefinite integrals when struve functions etc are implemented
# test a substitution
assert integrate(besselj(1, x**2)*x, x, meijerg=True) == \
-besselj(0, x**2)/2
def test_meijerg_eval():
from sympy import besseli, exp_polar
from sympy.abc import l
a = randcplx()
arg = x*exp_polar(k*pi*I)
expr1 = pi*meijerg([[], [(a + 1)/2]], [[a/2], [-a/2, (a + 1)/2]], arg**2/4)
expr2 = besseli(a, arg)
# Test that the two expressions agree for all arguments.
for x_ in [0.5, 1.5]:
for k_ in [0.0, 0.1, 0.3, 0.5, 0.8, 1, 5.751, 15.3]:
assert abs((expr1 - expr2).n(subs={x: x_, k: k_})) < 1e-10
assert abs((expr1 - expr2).n(subs={x: x_, k: -k_})) < 1e-10
# Test continuity independently
eps = 1e-13
expr2 = expr1.subs(k, l)
for x_ in [0.5, 1.5]:
for k_ in [0.5, S(1)/3, 0.25, 0.75, S(2)/3, 1.0, 1.5]:
assert abs((expr1 - expr2).n(
subs={x: x_, k: k_ + eps, l: k_ - eps})) < 1e-10
assert abs((expr1 - expr2).n(
subs={x: x_, k: -k_ + eps, l: -k_ - eps})) < 1e-10
expr = (meijerg(((0.5,), ()), ((0.5, 0, 0.5), ()), exp_polar(-I*pi)/4)
+ meijerg(((0.5,), ()), ((0.5, 0, 0.5), ()), exp_polar(I*pi)/4)) \
/(2*sqrt(pi))
assert (expr - pi/exp(1)).n(chop=True) == 0
def test_chi_noncentral():
k = Symbol("k", integer=True)
l = Symbol("l")
X = ChiNoncentral("x", k, l)
assert density(X)(x) == (x**k*l*(x*l)**(-k/2)*
exp(-x**2/2 - l**2/2)*besseli(k/2 - 1, x*l))
def test_chi_noncentral():
k = Symbol("k", integer=True)
l = Symbol("l")
X = ChiNoncentral("x", k, l)
assert density(X)(x) == (x**k*l*(x*l)**(-k/2)*
exp(-x**2/2 - l**2/2)*besseli(k/2 - 1, x*l))
def test_bessel():
from sympy import besselj, besseli
assert simplify(integrate(besselj(a, z) * besselj(b, z) / z, (z, 0, oo), meijerg=True, conds="none")) == 2 * sin(
pi * (a / 2 - b / 2)
) / (pi * (a - b) * (a + b))
assert simplify(integrate(besselj(a, z) * besselj(a, z) / z, (z, 0, oo), meijerg=True, conds="none")) == 1 / (2 * a)
# TODO more orthogonality integrals
assert simplify(
integrate(sin(z * x) * (x ** 2 - 1) ** (-(y + S(1) / 2)), (x, 1, oo), meijerg=True, conds="none")
* 2
/ ((z / 2) ** y * sqrt(pi) * gamma(S(1) / 2 - y))
) == besselj(y, z)
# Werner Rosenheinrich
# SOME INDEFINITE INTEGRALS OF BESSEL FUNCTIONS
assert integrate(x * besselj(0, x), x, meijerg=True) == x * besselj(1, x)
assert integrate(x * besseli(0, x), x, meijerg=True) == x * besseli(1, x)
# TODO can do higher powers, but come out as high order ... should they be
# reduced to order 0, 1?
assert integrate(besselj(1, x), x, meijerg=True) == -besselj(0, x)
assert integrate(besselj(1, x) ** 2 / x, x, meijerg=True) == -(besselj(0, x) ** 2 + besselj(1, x) ** 2) / 2
# TODO more besseli when tables are extended or recursive mellin works
assert (
integrate(besselj(0, x) ** 2 / x ** 2, x, meijerg=True)
== -2 * x * besselj(0, x) ** 2
- 2 * x * besselj(1, x) ** 2
+ 2 * besselj(0, x) * besselj(1, x)
- besselj(0, x) ** 2 / x
)
assert integrate(besselj(0, x) * besselj(1, x), x, meijerg=True) == -besselj(0, x) ** 2 / 2
assert integrate(x ** 2 * besselj(0, x) * besselj(1, x), x, meijerg=True) == x ** 2 * besselj(1, x) ** 2 / 2
assert integrate(besselj(0, x) * besselj(1, x) / x, x, meijerg=True) == (
x * besselj(0, x) ** 2 + x * besselj(1, x) ** 2 - besselj(0, x) * besselj(1, x)
)
# TODO how does besselj(0, a*x)*besselj(0, b*x) work?
# TODO how does besselj(0, x)**2*besselj(1, x)**2 work?
# TODO sin(x)*besselj(0, x) etc come out a mess
# TODO can x*log(x)*besselj(0, x) be done?
# TODO how does besselj(1, x)*besselj(0, x+a) work?
# TODO more indefinite integrals when struve functions etc are implemented
# test a substitution
assert integrate(besselj(1, x ** 2) * x, x, meijerg=True) == -besselj(0, x ** 2) / 2
def test_bessel_rand():
assert td(besselj(randcplx(), z), z)
assert td(bessely(randcplx(), z), z)
assert td(besseli(randcplx(), z), z)
assert td(besselk(randcplx(), z), z)
assert td(hankel1(randcplx(), z), z)
assert td(hankel2(randcplx(), z), z)
assert td(jn(randcplx(), z), z)
assert td(yn(randcplx(), z), z)
def test_bessel_rand():
assert td(besselj(randcplx(), z), z)
assert td(bessely(randcplx(), z), z)
assert td(besseli(randcplx(), z), z)
assert td(besselk(randcplx(), z), z)
assert td(hankel1(randcplx(), z), z)
assert td(hankel2(randcplx(), z), z)
assert td(jn(randcplx(), z), z)
assert td(yn(randcplx(), z), z)
def test_bessel_eval():
from sympy import I, Symbol
n, m, k = (
Symbol("n", integer=True),
Symbol("m"),
Symbol("k", integer=True, zero=False),
)
for f in [besselj, besseli]:
assert f(0, 0) is S.One
assert f(2.1, 0) is S.Zero
assert f(-3, 0) is S.Zero
assert f(-10.2, 0) is S.ComplexInfinity
assert f(1 + 3 * I, 0) is S.Zero
assert f(-3 + I, 0) is S.ComplexInfinity
assert f(-2 * I, 0) is S.NaN
assert f(n, 0) != S.One and f(n, 0) != S.Zero
assert f(m, 0) != S.One and f(m, 0) != S.Zero
assert f(k, 0) is S.Zero
assert bessely(0, 0) is S.NegativeInfinity
assert besselk(0, 0) is S.Infinity
for f in [bessely, besselk]:
assert f(1 + I, 0) is S.ComplexInfinity
assert f(I, 0) is S.NaN
for f in [besselj, bessely]:
assert f(m, S.Infinity) is S.Zero
assert f(m, S.NegativeInfinity) is S.Zero
for f in [besseli, besselk]:
assert f(m, I * S.Infinity) is S.Zero
assert f(m, I * S.NegativeInfinity) is S.Zero
for f in [besseli, besselk]:
assert f(-4, z) == f(4, z)
assert f(-3, z) == f(3, z)
assert f(-n, z) == f(n, z)
assert f(-m, z) != f(m, z)
for f in [besselj, bessely]:
assert f(-4, z) == f(4, z)
assert f(-3, z) == -f(3, z)
assert f(-n, z) == (-1)**n * f(n, z)
assert f(-m, z) != (-1)**m * f(m, z)
for f in [besselj, besseli]:
assert f(m, -z) == (-z)**m * z**(-m) * f(m, z)
assert besseli(2, -z) == besseli(2, z)
assert besseli(3, -z) == -besseli(3, z)
assert besselj(0, -z) == besselj(0, z)
assert besselj(1, -z) == -besselj(1, z)
assert besseli(0, I * z) == besselj(0, z)
assert besseli(1, I * z) == I * besselj(1, z)
assert besselj(3, I * z) == -I * besseli(3, z)
def test_massey_and_creation_of_simple_continued_fractions(self):
"""
unittests for our regular continued fractions
"""
rcf_constants = {
'e': e,
'bessel_ratio': besseli(1, 2) / besseli(0, 2),
'phi': phi
}
with mpmath.workdps(self.precision):
for c in rcf_constants:
with self.subTest(test_constant=c):
lhs = rcf_constants[c]
rhs = SimpleContinuedFraction.from_irrational_constant(
lambdify((), lhs, modules="mpmath"),
self.precision // 5)
shift_reg = massey.slow_massey(rhs.a_, 199)
self.assertLessEqual(len(shift_reg), 20)
self.compare(lhs, rhs, self.precision // 20)
def test_inverse_laplace_transform():
from sympy import sinh, cosh, besselj, besseli, simplify, factor_terms
ILT = inverse_laplace_transform
a, b, c, = symbols("a b c", positive=True)
t = symbols("t")
def simp_hyp(expr):
return factor_terms(expand_mul(expr)).rewrite(sin)
# just test inverses of all of the above
assert ILT(1 / s, s, t) == Heaviside(t)
assert ILT(1 / s ** 2, s, t) == t * Heaviside(t)
assert ILT(1 / s ** 5, s, t) == t ** 4 * Heaviside(t) / 24
assert ILT(exp(-a * s) / s, s, t) == Heaviside(t - a)
assert ILT(exp(-a * s) / (s + b), s, t) == exp(b * (a - t)) * Heaviside(-a + t)
assert ILT(a / (s ** 2 + a ** 2), s, t) == sin(a * t) * Heaviside(t)
assert ILT(s / (s ** 2 + a ** 2), s, t) == cos(a * t) * Heaviside(t)
# TODO is there a way around simp_hyp?
assert simp_hyp(ILT(a / (s ** 2 - a ** 2), s, t)) == sinh(a * t) * Heaviside(t)
assert simp_hyp(ILT(s / (s ** 2 - a ** 2), s, t)) == cosh(a * t) * Heaviside(t)
assert ILT(a / ((s + b) ** 2 + a ** 2), s, t) == exp(-b * t) * sin(
a * t
) * Heaviside(t)
assert ILT((s + b) / ((s + b) ** 2 + a ** 2), s, t) == exp(-b * t) * cos(
a * t
) * Heaviside(t)
# TODO sinh/cosh shifted come out a mess. also delayed trig is a mess
# TODO should this simplify further?
assert ILT(exp(-a * s) / s ** b, s, t) == (t - a) ** (b - 1) * Heaviside(
t - a
) / gamma(b)
assert ILT(exp(-a * s) / sqrt(1 + s ** 2), s, t) == Heaviside(t - a) * besselj(
0, a - t
) # note: besselj(0, x) is even
# XXX ILT turns these branch factor into trig functions ...
assert simplify(
ILT(
a ** b * (s + sqrt(s ** 2 - a ** 2)) ** (-b) / sqrt(s ** 2 - a ** 2), s, t
).rewrite(exp)
) == Heaviside(t) * besseli(b, a * t)
assert ILT(
a ** b * (s + sqrt(s ** 2 + a ** 2)) ** (-b) / sqrt(s ** 2 + a ** 2), s, t
).rewrite(exp) == Heaviside(t) * besselj(b, a * t)
assert ILT(1 / (s * sqrt(s + 1)), s, t) == Heaviside(t) * erf(sqrt(t))
# TODO can we make erf(t) work?
assert ILT(1 / (s ** 2 * (s ** 2 + 1)), s, t) == (t - sin(t)) * Heaviside(t)
assert ILT((s * eye(2) - Matrix([[1, 0], [0, 2]])).inv(), s, t) == Matrix(
[[exp(t) * Heaviside(t), 0], [0, exp(2 * t) * Heaviside(t)]]
)
def test_slow_expand():
def check(eq, ans):
return tn(eq, ans) and eq == ans
rn = randcplx(a=1, b=0, d=0, c=2)
for besselx in [besselj, bessely, besseli, besselk]:
ri = S(2 * randint(-11, 10) + 1) / 2 # half integer in [-21/2, 21/2]
assert tn(besselsimp(besselx(ri, z)), besselx(ri, z))
assert check(expand_func(besseli(rn, x)),
besseli(rn - 2, x) - 2 * (rn - 1) * besseli(rn - 1, x) / x)
assert check(expand_func(besseli(-rn, x)),
besseli(-rn + 2, x) + 2 * (-rn + 1) * besseli(-rn + 1, x) / x)
assert check(expand_func(besselj(rn, x)),
-besselj(rn - 2, x) + 2 * (rn - 1) * besselj(rn - 1, x) / x)
assert check(
expand_func(besselj(-rn, x)),
-besselj(-rn + 2, x) + 2 * (-rn + 1) * besselj(-rn + 1, x) / x)
assert check(expand_func(besselk(rn, x)),
besselk(rn - 2, x) + 2 * (rn - 1) * besselk(rn - 1, x) / x)
assert check(expand_func(besselk(-rn, x)),
besselk(-rn + 2, x) - 2 * (-rn + 1) * besselk(-rn + 1, x) / x)
assert check(expand_func(bessely(rn, x)),
-bessely(rn - 2, x) + 2 * (rn - 1) * bessely(rn - 1, x) / x)
assert check(
expand_func(bessely(-rn, x)),
-bessely(-rn + 2, x) + 2 * (-rn + 1) * bessely(-rn + 1, x) / x)
def test_rewrite():
assert besselj(n, z).rewrite(jn) == sqrt(2 * z / pi) * jn(n - S.Half, z)
assert bessely(n, z).rewrite(yn) == sqrt(2 * z / pi) * yn(n - S.Half, z)
assert besseli(n, z).rewrite(besselj) == \
exp(-I*n*pi/2)*besselj(n, polar_lift(I)*z)
assert besselj(n, z).rewrite(besseli) == \
exp(I*n*pi/2)*besseli(n, polar_lift(-I)*z)
nu = randcplx()
assert tn(besselj(nu, z), besselj(nu, z).rewrite(besseli), z)
assert tn(besselj(nu, z), besselj(nu, z).rewrite(bessely), z)
assert tn(besseli(nu, z), besseli(nu, z).rewrite(besselj), z)
assert tn(besseli(nu, z), besseli(nu, z).rewrite(bessely), z)
assert tn(bessely(nu, z), bessely(nu, z).rewrite(besselj), z)
assert tn(bessely(nu, z), bessely(nu, z).rewrite(besseli), z)
assert tn(besselk(nu, z), besselk(nu, z).rewrite(besselj), z)
assert tn(besselk(nu, z), besselk(nu, z).rewrite(besseli), z)
assert tn(besselk(nu, z), besselk(nu, z).rewrite(bessely), z)
# check that a rewrite was triggered, when the order is set to a generic
# symbol 'nu'
assert yn(nu, z) != yn(nu, z).rewrite(jn)
assert hn1(nu, z) != hn1(nu, z).rewrite(jn)
assert hn2(nu, z) != hn2(nu, z).rewrite(jn)
assert jn(nu, z) != jn(nu, z).rewrite(yn)
assert hn1(nu, z) != hn1(nu, z).rewrite(yn)
assert hn2(nu, z) != hn2(nu, z).rewrite(yn)
# rewriting spherical bessel functions (SBFs) w.r.t. besselj, bessely is
# not allowed if a generic symbol 'nu' is used as the order of the SBFs
# to avoid inconsistencies (the order of bessel[jy] is allowed to be
# complex-valued, whereas SBFs are defined only for integer orders)
order = nu
for f in (besselj, bessely):
assert hn1(order, z) == hn1(order, z).rewrite(f)
assert hn2(order, z) == hn2(order, z).rewrite(f)
assert jn(order, z).rewrite(besselj) == sqrt(2) * sqrt(pi) * sqrt(
1 / z) * besselj(order + S.Half, z) / 2
assert jn(order,
z).rewrite(bessely) == (-1)**nu * sqrt(2) * sqrt(pi) * sqrt(
1 / z) * bessely(-order - S.Half, z) / 2
# for integral orders rewriting SBFs w.r.t bessel[jy] is allowed
N = Symbol('n', integer=True)
ri = randint(-11, 10)
for order in (ri, N):
for f in (besselj, bessely):
assert yn(order, z) != yn(order, z).rewrite(f)
assert jn(order, z) != jn(order, z).rewrite(f)
assert hn1(order, z) != hn1(order, z).rewrite(f)
assert hn2(order, z) != hn2(order, z).rewrite(f)
for func, refunc in product((yn, jn, hn1, hn2),
(jn, yn, besselj, bessely)):
assert tn(func(ri, z), func(ri, z).rewrite(refunc), z)
def test_besselsimp():
from sympy import besselj, besseli, cosh, cosine_transform, bessely
assert besselsimp(exp(-I*pi*y/2)*besseli(y, z*exp_polar(I*pi/2))) == \
besselj(y, z)
assert besselsimp(exp(-I*pi*a/2)*besseli(a, 2*sqrt(x)*exp_polar(I*pi/2))) == \
besselj(a, 2*sqrt(x))
assert besselsimp(sqrt(2)*sqrt(pi)*x**Rational(1, 4)*exp(I*pi/4)*exp(-I*pi*a/2) *
besseli(Rational(-1, 2), sqrt(x)*exp_polar(I*pi/2)) *
besseli(a, sqrt(x)*exp_polar(I*pi/2))/2) == \
besselj(a, sqrt(x)) * cos(sqrt(x))
assert besselsimp(besseli(Rational(-1, 2), z)) == \
sqrt(2)*cosh(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besseli(a, z*exp_polar(-I*pi/2))) == \
exp(-I*pi*a/2)*besselj(a, z)
assert cosine_transform(1/t*sin(a/t), t, y) == \
sqrt(2)*sqrt(pi)*besselj(0, 2*sqrt(a)*sqrt(y))/2
assert besselsimp(x**2*(a*(-2*besselj(5*I, x) + besselj(-2 + 5*I, x) +
besselj(2 + 5*I, x)) + b*(-2*bessely(5*I, x) + bessely(-2 + 5*I, x) +
bessely(2 + 5*I, x)))/4 + x*(a*(besselj(-1 + 5*I, x)/2 - besselj(1 + 5*I, x)/2)
+ b*(bessely(-1 + 5*I, x)/2 - bessely(1 + 5*I, x)/2)) + (x**2 + 25)*(a*besselj(5*I, x)
+ b*bessely(5*I, x))) == 0
assert besselsimp(81*x**2*(a*(besselj(Rational(-5, 3), 9*x) - 2*besselj(Rational(1, 3), 9*x) + besselj(Rational(7, 3), 9*x))
+ b*(bessely(Rational(-5, 3), 9*x) - 2*bessely(Rational(1, 3), 9*x) + bessely(Rational(7, 3), 9*x)))/4 + x*(a*(9*besselj(Rational(-2, 3), 9*x)/2
- 9*besselj(Rational(4, 3), 9*x)/2) + b*(9*bessely(Rational(-2, 3), 9*x)/2 - 9*bessely(Rational(4, 3), 9*x)/2)) +
(81*x**2 - Rational(1, 9))*(a*besselj(Rational(1, 3), 9*x) + b*bessely(Rational(1, 3), 9*x))) == 0
assert besselsimp(besselj(a-1,x) + besselj(a+1, x) - 2*a*besselj(a, x)/x) == 0
assert besselsimp(besselj(a-1,x) + besselj(a+1, x) + besselj(a, x)) == (2*a + x)*besselj(a, x)/x
assert besselsimp(x**2* besselj(a,x) + x**3*besselj(a+1, x) + besselj(a+2, x)) == \
2*a*x*besselj(a + 1, x) + x**3*besselj(a + 1, x) - x**2*besselj(a + 2, x) + 2*x*besselj(a + 1, x) + besselj(a + 2, x)
def test_bessel_eval():
from sympy import I, Symbol
n, m, k = Symbol('n', integer=True), Symbol('m'), Symbol('k', integer=True, zero=False)
for f in [besselj, besseli]:
assert f(0, 0) == S.One
assert f(2.1, 0) == S.Zero
assert f(-3, 0) == S.Zero
assert f(-10.2, 0) == S.ComplexInfinity
assert f(1 + 3*I, 0) == S.Zero
assert f(-3 + I, 0) == S.ComplexInfinity
assert f(-2*I, 0) == S.NaN
assert f(n, 0) != S.One and f(n, 0) != S.Zero
assert f(m, 0) != S.One and f(m, 0) != S.Zero
assert f(k, 0) == S.Zero
assert bessely(0, 0) == S.NegativeInfinity
assert besselk(0, 0) == S.Infinity
for f in [bessely, besselk]:
assert f(1 + I, 0) == S.ComplexInfinity
assert f(I, 0) == S.NaN
for f in [besselj, bessely]:
assert f(m, S.Infinity) == S.Zero
assert f(m, S.NegativeInfinity) == S.Zero
for f in [besseli, besselk]:
assert f(m, I*S.Infinity) == S.Zero
assert f(m, I*S.NegativeInfinity) == S.Zero
for f in [besseli, besselk]:
assert f(-4, z) == f(4, z)
assert f(-3, z) == f(3, z)
assert f(-n, z) == f(n, z)
assert f(-m, z) != f(m, z)
for f in [besselj, bessely]:
assert f(-4, z) == f(4, z)
assert f(-3, z) == -f(3, z)
assert f(-n, z) == (-1)**n*f(n, z)
assert f(-m, z) != (-1)**m*f(m, z)
for f in [besselj, besseli]:
assert f(m, -z) == (-z)**m*z**(-m)*f(m, z)
assert besseli(2, -z) == besseli(2, z)
assert besseli(3, -z) == -besseli(3, z)
assert besselj(0, -z) == besselj(0, z)
assert besselj(1, -z) == -besselj(1, z)
assert besseli(0, I*z) == besselj(0, z)
assert besseli(1, I*z) == I*besselj(1, z)
assert besselj(3, I*z) == -I*besseli(3, z)
def test_hyperexpand_bases():
assert hyperexpand(hyper([2], [a], z)) == \
a + z**(-a + 1)*(-a**2 + 3*a + z*(a - 1) - 2)*exp(z)*lowergamma(a - 1, z) - 1
# TODO [a+1, a-S.Half], [2*a]
assert hyperexpand(hyper([1, 2], [3], z)) == -2/z - 2*log(-z + 1)/z**2
assert hyperexpand(hyper([S.Half, 2], [S(3)/2], z)) == \
-1/(2*z - 2) + atanh(sqrt(z))/sqrt(z)/2
assert hyperexpand(hyper([S(1)/2, S(1)/2], [S(5)/2], z)) == \
(-3*z + 3)/4/(z*sqrt(-z + 1)) \
+ (6*z - 3)*asin(sqrt(z))/(4*z**(S(3)/2))
assert hyperexpand(hyper([1, 2], [S(3)/2], z)) == -1/(2*z - 2) \
- asin(sqrt(z))/(sqrt(z)*(2*z - 2)*sqrt(-z + 1))
assert hyperexpand(hyper([-S.Half - 1, 1, 2], [S.Half, 3], z)) == \
sqrt(z)*(6*z/7 - S(6)/5)*atanh(sqrt(z)) \
+ (-30*z**2 + 32*z - 6)/35/z - 6*log(-z + 1)/(35*z**2)
assert hyperexpand(hyper([1+S.Half, 1, 1], [2, 2], z)) == \
-4*log(sqrt(-z + 1)/2 + S(1)/2)/z
# TODO hyperexpand(hyper([a], [2*a + 1], z))
# TODO [S.Half, a], [S(3)/2, a+1]
assert hyperexpand(hyper([2], [b, 1], z)) == \
z**(-b/2 + S(1)/2)*besseli(b - 1, 2*sqrt(z))*gamma(b) \
+ z**(-b/2 + 1)*besseli(b, 2*sqrt(z))*gamma(b)
def test_meromorphic():
assert besselj(2, x).is_meromorphic(x, 1) == True
assert besselj(2, x).is_meromorphic(x, 0) == True
assert besselj(2, x).is_meromorphic(x, oo) == False
assert besselj(S(2) / 3, x).is_meromorphic(x, 1) == True
assert besselj(S(2) / 3, x).is_meromorphic(x, 0) == False
assert besselj(S(2) / 3, x).is_meromorphic(x, oo) == False
assert besselj(x, 2 * x).is_meromorphic(x, 2) == False
assert besselk(0, x).is_meromorphic(x, 1) == True
assert besselk(2, x).is_meromorphic(x, 0) == True
assert besseli(0, x).is_meromorphic(x, 1) == True
assert besseli(2, x).is_meromorphic(x, 0) == True
assert bessely(0, x).is_meromorphic(x, 1) == True
assert bessely(0, x).is_meromorphic(x, 0) == False
assert bessely(2, x).is_meromorphic(x, 0) == True
assert hankel1(3, x**2 + 2 * x).is_meromorphic(x, 1) == True
assert hankel1(0, x).is_meromorphic(x, 0) == False
assert hankel2(11, 4).is_meromorphic(x, 5) == True
assert hn1(6, 7 * x**3 + 4).is_meromorphic(x, 7) == True
assert hn2(3, 2 * x).is_meromorphic(x, 9) == True
assert jn(5, 2 * x + 7).is_meromorphic(x, 4) == True
assert yn(8, x**2 + 11).is_meromorphic(x, 6) == True
def test_hyperexpand_bases():
assert hyperexpand(hyper([2], [a], z)) == \
a + z**(-a + 1)*(-a**2 + 3*a + z*(a - 1) - 2)*exp(z)*lowergamma(a - 1, z) - 1
# TODO [a+1, a-S.Half], [2*a]
assert hyperexpand(hyper([1, 2], [3], z)) == -2/z - 2*log(-z + 1)/z**2
assert hyperexpand(hyper([S.Half, 2], [S(3)/2], z)) == \
-1/(2*z - 2) + log((z**(S(1)/2) + 1)/(-z**(S(1)/2) + 1))/(4*z**(S(1)/2))
assert hyperexpand(hyper([S(1)/2, S(1)/2], [S(5)/2], z)) == \
(-3*z + 3)/(4*z*(-z + 1)**(S(1)/2)) \
+ (6*z - 3)*asin(z**(S(1)/2))/(4*z**(S(3)/2))
assert hyperexpand(hyper([1, 2], [S(3)/2], z)) == -1/(2*z - 2) \
- asin(z**(S(1)/2))/(z**(S(1)/2)*(2*z - 2)*(-z + 1)**(S(1)/2))
assert hyperexpand(hyper([-S.Half - 1, 1, 2], [S.Half, 3], z)) == \
z**(S(1)/2)*(6*z/7 - S(6)/5)*atanh(z**(S(1)/2)) \
+ (-30*z**2 + 32*z - 6)/(35*z) - 6*log(-z + 1)/(35*z**2)
assert hyperexpand(hyper([1+S.Half, 1, 1], [2, 2], z)) == \
-4*log((-z + 1)**(S(1)/2)/2 + S(1)/2)/z
# TODO hyperexpand(hyper([a], [2*a + 1], z))
# TODO [S.Half, a], [S(3)/2, a+1]
assert hyperexpand(hyper([2], [b, 1], z)) == \
z**(-b/2 + S(1)/2)*besseli(b - 1, 2*z**(S(1)/2))*gamma(b) \
+ z**(-b/2 + 1)*besseli(b, 2*z**(S(1)/2))*gamma(b)
def test_rewrite():
from sympy import polar_lift, exp, I
assert besselj(n, z).rewrite(jn) == sqrt(2*z/pi)*jn(n - S(1)/2, z)
assert bessely(n, z).rewrite(yn) == sqrt(2*z/pi)*yn(n - S(1)/2, z)
assert besseli(n, z).rewrite(besselj) == \
exp(-I*n*pi/2)*besselj(n, polar_lift(I)*z)
assert besselj(n, z).rewrite(besseli) == \
exp(I*n*pi/2)*besseli(n, polar_lift(-I)*z)
nu = randcplx()
assert tn(besselj(nu, z), besselj(nu, z).rewrite(besseli), z)
assert tn(besselj(nu, z), besselj(nu, z).rewrite(bessely), z)
assert tn(besseli(nu, z), besseli(nu, z).rewrite(besselj), z)
assert tn(besseli(nu, z), besseli(nu, z).rewrite(bessely), z)
assert tn(bessely(nu, z), bessely(nu, z).rewrite(besselj), z)
assert tn(bessely(nu, z), bessely(nu, z).rewrite(besseli), z)
assert tn(besselk(nu, z), besselk(nu, z).rewrite(besselj), z)
assert tn(besselk(nu, z), besselk(nu, z).rewrite(besseli), z)
assert tn(besselk(nu, z), besselk(nu, z).rewrite(bessely), z)
# check that a rewrite was triggered, when the order is set to a generic
# symbol 'nu'
assert yn(nu, z) != yn(nu, z).rewrite(jn)
assert hn1(nu, z) != hn1(nu, z).rewrite(jn)
assert hn2(nu, z) != hn2(nu, z).rewrite(jn)
assert jn(nu, z) != jn(nu, z).rewrite(yn)
assert hn1(nu, z) != hn1(nu, z).rewrite(yn)
assert hn2(nu, z) != hn2(nu, z).rewrite(yn)
# rewriting spherical bessel functions (SBFs) w.r.t. besselj, bessely is
# not allowed if a generic symbol 'nu' is used as the order of the SBFs
# to avoid inconsistencies (the order of bessel[jy] is allowed to be
# complex-valued, whereas SBFs are defined only for integer orders)
order = nu
for f in (besselj, bessely):
assert hn1(order, z) == hn1(order, z).rewrite(f)
assert hn2(order, z) == hn2(order, z).rewrite(f)
assert jn(order, z).rewrite(besselj) == sqrt(2)*sqrt(pi)*sqrt(1/z)*besselj(order + S(1)/2, z)/2
assert jn(order, z).rewrite(bessely) == (-1)**nu*sqrt(2)*sqrt(pi)*sqrt(1/z)*bessely(-order - S(1)/2, z)/2
# for integral orders rewriting SBFs w.r.t bessel[jy] is allowed
N = Symbol('n', integer=True)
ri = randint(-11, 10)
for order in (ri, N):
for f in (besselj, bessely):
assert yn(order, z) != yn(order, z).rewrite(f)
assert jn(order, z) != jn(order, z).rewrite(f)
assert hn1(order, z) != hn1(order, z).rewrite(f)
assert hn2(order, z) != hn2(order, z).rewrite(f)
for func, refunc in product((yn, jn, hn1, hn2),
(jn, yn, besselj, bessely)):
assert tn(func(ri, z), func(ri, z).rewrite(refunc), z)
def test_skellam():
mu1 = Symbol('mu1')
mu2 = Symbol('mu2')
z = Symbol('z')
X = Skellam('x', mu1, mu2)
assert density(X)(z) == (mu1/mu2)**(z/2) * \
exp(-mu1 - mu2)*besseli(z, 2*sqrt(mu1*mu2))
assert skewness(X).expand() == mu1/(mu1*sqrt(mu1 + mu2) + mu2 *
sqrt(mu1 + mu2)) - mu2/(mu1*sqrt(mu1 + mu2) + mu2*sqrt(mu1 + mu2))
assert variance(X).expand() == mu1 + mu2
assert E(X) == mu1 - mu2
assert characteristic_function(X)(z) == exp(
mu1*exp(I*z) - mu1 - mu2 + mu2*exp(-I*z))
assert moment_generating_function(X)(z) == exp(
mu1*exp(z) - mu1 - mu2 + mu2*exp(-z))
def test_inverse_laplace_transform():
from sympy import sinh, cosh, besselj, besseli, simplify, factor_terms
ILT = inverse_laplace_transform
a, b, c, = symbols("a b c", positive=True, finite=True)
t = symbols("t")
def simp_hyp(expr):
return factor_terms(expand_mul(expr)).rewrite(sin)
# just test inverses of all of the above
assert ILT(1 / s, s, t) == Heaviside(t)
assert ILT(1 / s ** 2, s, t) == t * Heaviside(t)
assert ILT(1 / s ** 5, s, t) == t ** 4 * Heaviside(t) / 24
assert ILT(exp(-a * s) / s, s, t) == Heaviside(t - a)
assert ILT(exp(-a * s) / (s + b), s, t) == exp(b * (a - t)) * Heaviside(-a + t)
assert ILT(a / (s ** 2 + a ** 2), s, t) == sin(a * t) * Heaviside(t)
assert ILT(s / (s ** 2 + a ** 2), s, t) == cos(a * t) * Heaviside(t)
# TODO is there a way around simp_hyp?
assert simp_hyp(ILT(a / (s ** 2 - a ** 2), s, t)) == sinh(a * t) * Heaviside(t)
assert simp_hyp(ILT(s / (s ** 2 - a ** 2), s, t)) == cosh(a * t) * Heaviside(t)
assert ILT(a / ((s + b) ** 2 + a ** 2), s, t) == exp(-b * t) * sin(a * t) * Heaviside(t)
assert ILT((s + b) / ((s + b) ** 2 + a ** 2), s, t) == exp(-b * t) * cos(a * t) * Heaviside(t)
# TODO sinh/cosh shifted come out a mess. also delayed trig is a mess
# TODO should this simplify further?
assert ILT(exp(-a * s) / s ** b, s, t) == (t - a) ** (b - 1) * Heaviside(t - a) / gamma(b)
assert ILT(exp(-a * s) / sqrt(1 + s ** 2), s, t) == Heaviside(t - a) * besselj(
0, a - t
) # note: besselj(0, x) is even
# XXX ILT turns these branch factor into trig functions ...
assert simplify(
ILT(a ** b * (s + sqrt(s ** 2 - a ** 2)) ** (-b) / sqrt(s ** 2 - a ** 2), s, t).rewrite(exp)
) == Heaviside(t) * besseli(b, a * t)
assert ILT(a ** b * (s + sqrt(s ** 2 + a ** 2)) ** (-b) / sqrt(s ** 2 + a ** 2), s, t).rewrite(exp) == Heaviside(
t
) * besselj(b, a * t)
assert ILT(1 / (s * sqrt(s + 1)), s, t) == Heaviside(t) * erf(sqrt(t))
# TODO can we make erf(t) work?
assert ILT(1 / (s ** 2 * (s ** 2 + 1)), s, t) == (t - sin(t)) * Heaviside(t)
assert ILT((s * eye(2) - Matrix([[1, 0], [0, 2]])).inv(), s, t) == Matrix(
[[exp(t) * Heaviside(t), 0], [0, exp(2 * t) * Heaviside(t)]]
)
def test_besselsimp():
from sympy import besselj, besseli, besselk, bessely, jn, yn, exp_polar, cosh
assert besselsimp(exp(-I*pi*y/2)*besseli(y, z*exp_polar(I*pi/2))) == \
besselj(y, z)
assert besselsimp(exp(-I*pi*a/2)*besseli(a, 2*sqrt(x)*exp_polar(I*pi/2))) == \
besselj(a, 2*sqrt(x))
assert besselsimp(sqrt(2)*sqrt(pi)*x**(S(1)/4)*exp(I*pi/4)*exp(-I*pi*a/2) * \
besseli(-S(1)/2, sqrt(x)*exp_polar(I*pi/2)) * \
besseli(a, sqrt(x)*exp_polar(I*pi/2))/2) == \
besselj(a, sqrt(x)) * cos(sqrt(x))
assert besselsimp(besseli(S(-1)/2, z)) == sqrt(2)*cosh(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besseli(a, z*exp_polar(-I*pi/2))) == exp(-I*pi*a/2)*besselj(a, z)
def test_besselsimp():
from sympy import besselj, besseli, besselk, bessely, jn, yn, exp_polar, cosh
assert besselsimp(exp(-I*pi*y/2)*besseli(y, z*exp_polar(I*pi/2))) == \
besselj(y, z)
assert besselsimp(exp(-I*pi*a/2)*besseli(a, 2*sqrt(x)*exp_polar(I*pi/2))) == \
besselj(a, 2*sqrt(x))
assert besselsimp(sqrt(2)*sqrt(pi)*x**(S(1)/4)*exp(I*pi/4)*exp(-I*pi*a/2) * \
besseli(-S(1)/2, sqrt(x)*exp_polar(I*pi/2)) * \
besseli(a, sqrt(x)*exp_polar(I*pi/2))/2) == \
besselj(a, sqrt(x)) * cos(sqrt(x))
assert besselsimp(besseli(S(-1)/2, z)) == sqrt(2)*cosh(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besseli(a, z*exp_polar(-I*pi/2))) == exp(-I*pi*a/2)*besselj(a, z)
def test_chi_noncentral():
k = Symbol("k", integer=True)
l = Symbol("l")
X = ChiNoncentral("x", k, l)
assert density(X)(x) == (x**k*l*(x*l)**(-k/2)*
exp(-x**2/2 - l**2/2)*besseli(k/2 - 1, x*l))
k = Symbol("k", integer=True, positive=False)
raises(ValueError, lambda: ChiNoncentral('x', k, l))
k = Symbol("k", integer=True, positive=True)
l = Symbol("l", nonpositive=True)
raises(ValueError, lambda: ChiNoncentral('x', k, l))
k = Symbol("k", integer=False)
l = Symbol("l", positive=True)
raises(ValueError, lambda: ChiNoncentral('x', k, l))
def test_chi_noncentral():
k = Symbol("k", integer=True)
l = Symbol("l")
X = ChiNoncentral("x", k, l)
assert density(X)(x) == (x**k*l*(x*l)**(-k/2)*
exp(-x**2/2 - l**2/2)*besseli(k/2 - 1, x*l))
k = Symbol("k", integer=True, positive=False)
raises(ValueError, lambda: ChiNoncentral('x', k, l))
k = Symbol("k", integer=True, positive=True)
l = Symbol("l", positive=False)
raises(ValueError, lambda: ChiNoncentral('x', k, l))
k = Symbol("k", integer=False)
l = Symbol("l", positive=True)
raises(ValueError, lambda: ChiNoncentral('x', k, l))
def test_inverse_laplace_transform():
from sympy import (expand, sinh, cosh, besselj, besseli, exp_polar,
unpolarify, simplify)
ILT = inverse_laplace_transform
a, b, c, = symbols('a b c', positive=True)
t = symbols('t')
def simp_hyp(expr):
return expand(expand(expr).rewrite(sin))
# just test inverses of all of the above
assert ILT(1 / s, s, t) == Heaviside(t)
assert ILT(1 / s**2, s, t) == t * Heaviside(t)
assert ILT(1 / s**5, s, t) == t**4 * Heaviside(t) / factorial(4)
assert ILT(exp(-a * s) / s, s, t) == Heaviside(t - a)
assert ILT(exp(-a * s) / (s + b), s,
t) == exp(-b * (-a + t)) * Heaviside(t - a)
assert ILT(a / (s**2 + a**2), s, t) == sin(a * t) * Heaviside(t)
assert ILT(s / (s**2 + a**2), s, t) == cos(a * t) * Heaviside(t)
# TODO is there a way around simp_hyp?
assert simp_hyp(ILT(a / (s**2 - a**2), s, t)) == sinh(a * t) * Heaviside(t)
assert simp_hyp(ILT(s / (s**2 - a**2), s, t)) == cosh(a * t) * Heaviside(t)
assert ILT(a / ((s + b)**2 + a**2), s,
t) == exp(-b * t) * sin(a * t) * Heaviside(t)
assert ILT((s + b) / ((s + b)**2 + a**2), s,
t) == exp(-b * t) * cos(a * t) * Heaviside(t)
# TODO sinh/cosh shifted come out a mess. also delayed trig is a mess
# TODO should this simplify further?
assert ILT(exp(-a*s)/s**b, s, t) == \
(t - a)**(b - 1)*Heaviside(t - a)/gamma(b)
assert ILT(exp(-a*s)/sqrt(1 + s**2), s, t) == \
Heaviside(t - a)*besselj(0, a - t) # note: besselj(0, x) is even
# TODO besselsimp would be good to have
# XXX ILT turns these branch factor into trig functions ...
assert simplify(ILT(a**b*(s + sqrt(s**2 - a**2))**(-b)/sqrt(s**2 - a**2),
s, t).rewrite(exp)) == \
exp(-I*pi*b)*Heaviside(t)*besseli(b, a*t*exp_polar(I*pi))
assert ILT(a**b*(s + sqrt(s**2 + a**2))**(-b)/sqrt(s**2 + a**2),
s, t).rewrite(besselj).rewrite(exp) == \
exp(-I*pi*b)*Heaviside(t)*besselj(b, a*t*exp_polar(I*pi))
assert ILT(1 / (s * sqrt(s + 1)), s, t) == Heaviside(t) * erf(sqrt(t))
def test_inverse_laplace_transform():
from sympy import (expand, sinh, cosh, besselj, besseli, exp_polar,
unpolarify, simplify)
ILT = inverse_laplace_transform
a, b, c, = symbols('a b c', positive=True)
t = symbols('t')
def simp_hyp(expr):
return expand(expand(expr).rewrite(sin))
# just test inverses of all of the above
assert ILT(1/s, s, t) == Heaviside(t)
assert ILT(1/s**2, s, t) == t*Heaviside(t)
assert ILT(1/s**5, s, t) == t**4*Heaviside(t)/24
assert ILT(exp(-a*s)/s, s, t) == Heaviside(t - a)
assert ILT(exp(-a*s)/(s + b), s, t) == exp(b*(a - t))*Heaviside(-a + t)
assert ILT(a/(s**2 + a**2), s, t) == sin(a*t)*Heaviside(t)
assert ILT(s/(s**2 + a**2), s, t) == cos(a*t)*Heaviside(t)
# TODO is there a way around simp_hyp?
assert simp_hyp(ILT(a/(s**2 - a**2), s, t)) == sinh(a*t)*Heaviside(t)
assert simp_hyp(ILT(s/(s**2 - a**2), s, t)) == cosh(a*t)*Heaviside(t)
assert ILT(a/((s + b)**2 + a**2), s, t) == exp(-b*t)*sin(a*t)*Heaviside(t)
assert ILT(
(s + b)/((s + b)**2 + a**2), s, t) == exp(-b*t)*cos(a*t)*Heaviside(t)
# TODO sinh/cosh shifted come out a mess. also delayed trig is a mess
# TODO should this simplify further?
assert ILT(exp(-a*s)/s**b, s, t) == \
(t - a)**(b - 1)*Heaviside(t - a)/gamma(b)
assert ILT(exp(-a*s)/sqrt(1 + s**2), s, t) == \
Heaviside(t - a)*besselj(0, a - t) # note: besselj(0, x) is even
# XXX ILT turns these branch factor into trig functions ...
assert simplify(ILT(a**b*(s + sqrt(s**2 - a**2))**(-b)/sqrt(s**2 - a**2),
s, t).rewrite(exp)) == \
Heaviside(t)*besseli(b, a*t)
assert ILT(a**b*(s + sqrt(s**2 + a**2))**(-b)/sqrt(s**2 + a**2),
s, t).rewrite(exp) == \
Heaviside(t)*besselj(b, a*t)
assert ILT(1/(s*sqrt(s + 1)), s, t) == Heaviside(t)*erf(sqrt(t))
def test_besselsimp():
from sympy import besselj, besseli, exp_polar, cosh, cosine_transform
assert besselsimp(exp(-I*pi*y/2)*besseli(y, z*exp_polar(I*pi/2))) == \
besselj(y, z)
assert besselsimp(exp(-I*pi*a/2)*besseli(a, 2*sqrt(x)*exp_polar(I*pi/2))) == \
besselj(a, 2*sqrt(x))
assert besselsimp(sqrt(2)*sqrt(pi)*x**(S(1)/4)*exp(I*pi/4)*exp(-I*pi*a/2) *
besseli(-S(1)/2, sqrt(x)*exp_polar(I*pi/2)) *
besseli(a, sqrt(x)*exp_polar(I*pi/2))/2) == \
besselj(a, sqrt(x)) * cos(sqrt(x))
assert besselsimp(besseli(S(-1)/2, z)) == \
sqrt(2)*cosh(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besseli(a, z*exp_polar(-I*pi/2))) == \
exp(-I*pi*a/2)*besselj(a, z)
assert cosine_transform(1/t*sin(a/t), t, y) == \
sqrt(2)*sqrt(pi)*besselj(0, 2*sqrt(a)*sqrt(y))/2
def test_besselsimp():
from sympy import besselj, besseli, exp_polar, cosh, cosine_transform
assert besselsimp(exp(-I*pi*y/2)*besseli(y, z*exp_polar(I*pi/2))) == \
besselj(y, z)
assert besselsimp(exp(-I*pi*a/2)*besseli(a, 2*sqrt(x)*exp_polar(I*pi/2))) == \
besselj(a, 2*sqrt(x))
assert besselsimp(sqrt(2)*sqrt(pi)*x**(S(1)/4)*exp(I*pi/4)*exp(-I*pi*a/2) *
besseli(-S(1)/2, sqrt(x)*exp_polar(I*pi/2)) *
besseli(a, sqrt(x)*exp_polar(I*pi/2))/2) == \
besselj(a, sqrt(x)) * cos(sqrt(x))
assert besselsimp(besseli(S(-1)/2, z)) == \
sqrt(2)*cosh(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besseli(a, z*exp_polar(-I*pi/2))) == \
exp(-I*pi*a/2)*besselj(a, z)
assert cosine_transform(1/t*sin(a/t), t, y) == \
sqrt(2)*sqrt(pi)*besselj(0, 2*sqrt(a)*sqrt(y))/2
def test_besselsimp():
from sympy import besselj, besseli, exp_polar, cosh, cosine_transform, bessely
assert besselsimp(exp(-I*pi*y/2)*besseli(y, z*exp_polar(I*pi/2))) == \
besselj(y, z)
assert besselsimp(exp(-I*pi*a/2)*besseli(a, 2*sqrt(x)*exp_polar(I*pi/2))) == \
besselj(a, 2*sqrt(x))
assert besselsimp(sqrt(2)*sqrt(pi)*x**(S(1)/4)*exp(I*pi/4)*exp(-I*pi*a/2) *
besseli(-S(1)/2, sqrt(x)*exp_polar(I*pi/2)) *
besseli(a, sqrt(x)*exp_polar(I*pi/2))/2) == \
besselj(a, sqrt(x)) * cos(sqrt(x))
assert besselsimp(besseli(S(-1)/2, z)) == \
sqrt(2)*cosh(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besseli(a, z*exp_polar(-I*pi/2))) == \
exp(-I*pi*a/2)*besselj(a, z)
assert cosine_transform(1/t*sin(a/t), t, y) == \
sqrt(2)*sqrt(pi)*besselj(0, 2*sqrt(a)*sqrt(y))/2
assert besselsimp(
x**2 * (a * (-2 * besselj(5 * I, x) + besselj(-2 + 5 * I, x) +
besselj(2 + 5 * I, x)) + b *
(-2 * bessely(5 * I, x) + bessely(-2 + 5 * I, x) +
bessely(2 + 5 * I, x))) / 4 + x *
(a * (besselj(-1 + 5 * I, x) / 2 - besselj(1 + 5 * I, x) / 2) + b *
(bessely(-1 + 5 * I, x) / 2 - bessely(1 + 5 * I, x) / 2)) +
(x**2 + 25) * (a * besselj(5 * I, x) + b * bessely(5 * I, x))) == 0
assert besselsimp(
81 * x**2 *
(a * (besselj(-S(5) / 3, 9 * x) - 2 * besselj(S(1) / 3, 9 * x) +
besselj(S(7) / 3, 9 * x)) + b *
(bessely(-S(5) / 3, 9 * x) - 2 * bessely(S(1) / 3, 9 * x) +
bessely(S(7) / 3, 9 * x))) / 4 + x *
(a * (9 * besselj(-S(2) / 3, 9 * x) / 2 -
9 * besselj(S(4) / 3, 9 * x) / 2) + b *
(9 * bessely(-S(2) / 3, 9 * x) / 2 - 9 * bessely(S(4) / 3, 9 * x) / 2)
) + (81 * x**2 - S(1) / 9) *
(a * besselj(S(1) / 3, 9 * x) + b * bessely(S(1) / 3, 9 * x))) == 0
assert besselsimp(
besselj(a - 1, x) + besselj(a + 1, x) - 2 * a * besselj(a, x) / x) == 0
assert besselsimp(besselj(a - 1, x) + besselj(a + 1, x) +
besselj(a, x)) == (2 * a + x) * besselj(a, x) / x
assert besselsimp(x**2* besselj(a,x) + x**3*besselj(a+1, x) + besselj(a+2, x)) == \
2*a*x*besselj(a + 1, x) + x**3*besselj(a + 1, x) - x**2*besselj(a + 2, x) + 2*x*besselj(a + 1, x) + besselj(a + 2, x)
def test_probability():
# various integrals from probability theory
from sympy.abc import x, y
from sympy import symbols, Symbol, Abs, expand_mul, combsimp, powsimp, sin
mu1, mu2 = symbols('mu1 mu2', real=True, nonzero=True, finite=True)
sigma1, sigma2 = symbols('sigma1 sigma2',
real=True,
nonzero=True,
finite=True,
positive=True)
rate = Symbol('lambda', real=True, positive=True, finite=True)
def normal(x, mu, sigma):
return 1 / sqrt(2 * pi * sigma**2) * exp(-(x - mu)**2 / 2 / sigma**2)
def exponential(x, rate):
return rate * exp(-rate * x)
assert integrate(normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) == 1
assert integrate(x*normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) == \
mu1
assert integrate(x**2*normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) \
== mu1**2 + sigma1**2
assert integrate(x**3*normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) \
== mu1**3 + 3*mu1*sigma1**2
assert integrate(normal(x, mu1, sigma1) * normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo),
meijerg=True) == 1
assert integrate(x * normal(x, mu1, sigma1) * normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo),
meijerg=True) == mu1
assert integrate(y * normal(x, mu1, sigma1) * normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo),
meijerg=True) == mu2
assert integrate(x * y * normal(x, mu1, sigma1) * normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo),
meijerg=True) == mu1 * mu2
assert integrate(
(x + y + 1) * normal(x, mu1, sigma1) * normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo),
meijerg=True) == 1 + mu1 + mu2
assert integrate((x + y - 1)*normal(x, mu1, sigma1)*normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo), meijerg=True) == \
-1 + mu1 + mu2
i = integrate(x**2 * normal(x, mu1, sigma1) * normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo),
meijerg=True)
assert not i.has(Abs)
assert simplify(i) == mu1**2 + sigma1**2
assert integrate(y**2*normal(x, mu1, sigma1)*normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo), meijerg=True) == \
sigma2**2 + mu2**2
assert integrate(exponential(x, rate), (x, 0, oo), meijerg=True) == 1
assert integrate(x*exponential(x, rate), (x, 0, oo), meijerg=True) == \
1/rate
assert integrate(x**2*exponential(x, rate), (x, 0, oo), meijerg=True) == \
2/rate**2
def E(expr):
res1 = integrate(expr * exponential(x, rate) * normal(y, mu1, sigma1),
(x, 0, oo), (y, -oo, oo),
meijerg=True)
res2 = integrate(expr * exponential(x, rate) * normal(y, mu1, sigma1),
(y, -oo, oo), (x, 0, oo),
meijerg=True)
assert expand_mul(res1) == expand_mul(res2)
return res1
assert E(1) == 1
assert E(x * y) == mu1 / rate
assert E(x * y**2) == mu1**2 / rate + sigma1**2 / rate
ans = sigma1**2 + 1 / rate**2
assert simplify(E((x + y + 1)**2) - E(x + y + 1)**2) == ans
assert simplify(E((x + y - 1)**2) - E(x + y - 1)**2) == ans
assert simplify(E((x + y)**2) - E(x + y)**2) == ans
# Beta' distribution
alpha, beta = symbols('alpha beta', positive=True)
betadist = x**(alpha - 1)*(1 + x)**(-alpha - beta)*gamma(alpha + beta) \
/gamma(alpha)/gamma(beta)
assert integrate(betadist, (x, 0, oo), meijerg=True) == 1
i = integrate(x * betadist, (x, 0, oo), meijerg=True, conds='separate')
assert (combsimp(i[0]), i[1]) == (alpha / (beta - 1), 1 < beta)
j = integrate(x**2 * betadist, (x, 0, oo), meijerg=True, conds='separate')
assert j[1] == (1 < beta - 1)
assert combsimp(j[0] - i[0]**2) == (alpha + beta - 1)*alpha \
/(beta - 2)/(beta - 1)**2
# Beta distribution
# NOTE: this is evaluated using antiderivatives. It also tests that
# meijerint_indefinite returns the simplest possible answer.
a, b = symbols('a b', positive=True)
betadist = x**(a - 1) * (-x + 1)**(b - 1) * gamma(a + b) / (gamma(a) *
gamma(b))
assert simplify(integrate(betadist, (x, 0, 1), meijerg=True)) == 1
assert simplify(integrate(x*betadist, (x, 0, 1), meijerg=True)) == \
a/(a + b)
assert simplify(integrate(x**2*betadist, (x, 0, 1), meijerg=True)) == \
a*(a + 1)/(a + b)/(a + b + 1)
assert simplify(integrate(x**y*betadist, (x, 0, 1), meijerg=True)) == \
gamma(a + b)*gamma(a + y)/gamma(a)/gamma(a + b + y)
# Chi distribution
k = Symbol('k', integer=True, positive=True)
chi = 2**(1 - k / 2) * x**(k - 1) * exp(-x**2 / 2) / gamma(k / 2)
assert powsimp(integrate(chi, (x, 0, oo), meijerg=True)) == 1
assert simplify(integrate(x*chi, (x, 0, oo), meijerg=True)) == \
sqrt(2)*gamma((k + 1)/2)/gamma(k/2)
assert simplify(integrate(x**2 * chi, (x, 0, oo), meijerg=True)) == k
# Chi^2 distribution
chisquared = 2**(-k / 2) / gamma(k / 2) * x**(k / 2 - 1) * exp(-x / 2)
assert powsimp(integrate(chisquared, (x, 0, oo), meijerg=True)) == 1
assert simplify(integrate(x * chisquared, (x, 0, oo), meijerg=True)) == k
assert simplify(integrate(x**2*chisquared, (x, 0, oo), meijerg=True)) == \
k*(k + 2)
assert combsimp(
integrate(((x - k) / sqrt(2 * k))**3 * chisquared, (x, 0, oo),
meijerg=True)) == 2 * sqrt(2) / sqrt(k)
# Dagum distribution
a, b, p = symbols('a b p', positive=True)
# XXX (x/b)**a does not work
dagum = a * p / x * (x / b)**(a * p) / (1 + x**a / b**a)**(p + 1)
assert simplify(integrate(dagum, (x, 0, oo), meijerg=True)) == 1
# XXX conditions are a mess
arg = x * dagum
assert simplify(integrate(
arg, (x, 0, oo), meijerg=True,
conds='none')) == a * b * gamma(1 - 1 / a) * gamma(p + 1 + 1 / a) / (
(a * p + 1) * gamma(p))
assert simplify(integrate(
x * arg, (x, 0, oo), meijerg=True,
conds='none')) == a * b**2 * gamma(1 -
2 / a) * gamma(p + 1 + 2 / a) / (
(a * p + 2) * gamma(p))
# F-distribution
d1, d2 = symbols('d1 d2', positive=True)
f = sqrt(((d1*x)**d1 * d2**d2)/(d1*x + d2)**(d1 + d2))/x \
/gamma(d1/2)/gamma(d2/2)*gamma((d1 + d2)/2)
assert simplify(integrate(f, (x, 0, oo), meijerg=True)) == 1
# TODO conditions are a mess
assert simplify(integrate(x * f, (x, 0, oo), meijerg=True,
conds='none')) == d2 / (d2 - 2)
assert simplify(
integrate(x**2 * f, (x, 0, oo), meijerg=True,
conds='none')) == d2**2 * (d1 + 2) / d1 / (d2 - 4) / (d2 - 2)
# TODO gamma, rayleigh
# inverse gaussian
lamda, mu = symbols('lamda mu', positive=True)
dist = sqrt(lamda / 2 / pi) * x**(-S(3) / 2) * exp(
-lamda * (x - mu)**2 / x / 2 / mu**2)
mysimp = lambda expr: simplify(expr.rewrite(exp))
assert mysimp(integrate(dist, (x, 0, oo))) == 1
assert mysimp(integrate(x * dist, (x, 0, oo))) == mu
assert mysimp(integrate((x - mu)**2 * dist, (x, 0, oo))) == mu**3 / lamda
assert mysimp(integrate((x - mu)**3 * dist,
(x, 0, oo))) == 3 * mu**5 / lamda**2
# Levi
c = Symbol('c', positive=True)
assert integrate(
sqrt(c / 2 / pi) * exp(-c / 2 / (x - mu)) / (x - mu)**S('3/2'),
(x, mu, oo)) == 1
# higher moments oo
# log-logistic
distn = (beta/alpha)*x**(beta - 1)/alpha**(beta - 1)/ \
(1 + x**beta/alpha**beta)**2
assert simplify(integrate(distn, (x, 0, oo))) == 1
# NOTE the conditions are a mess, but correctly state beta > 1
assert simplify(integrate(x*distn, (x, 0, oo), conds='none')) == \
pi*alpha/beta/sin(pi/beta)
# (similar comment for conditions applies)
assert simplify(integrate(x**y*distn, (x, 0, oo), conds='none')) == \
pi*alpha**y*y/beta/sin(pi*y/beta)
# weibull
k = Symbol('k', positive=True)
n = Symbol('n', positive=True)
distn = k / lamda * (x / lamda)**(k - 1) * exp(-(x / lamda)**k)
assert simplify(integrate(distn, (x, 0, oo))) == 1
assert simplify(integrate(x**n*distn, (x, 0, oo))) == \
lamda**n*gamma(1 + n/k)
# rice distribution
from sympy import besseli
nu, sigma = symbols('nu sigma', positive=True)
rice = x / sigma**2 * exp(-(x**2 + nu**2) / 2 / sigma**2) * besseli(
0, x * nu / sigma**2)
assert integrate(rice, (x, 0, oo), meijerg=True) == 1
# can someone verify higher moments?
# Laplace distribution
mu = Symbol('mu', real=True)
b = Symbol('b', positive=True)
laplace = exp(-abs(x - mu) / b) / 2 / b
assert integrate(laplace, (x, -oo, oo), meijerg=True) == 1
assert integrate(x * laplace, (x, -oo, oo), meijerg=True) == mu
assert integrate(x**2*laplace, (x, -oo, oo), meijerg=True) == \
2*b**2 + mu**2
# TODO are there other distributions supported on (-oo, oo) that we can do?
# misc tests
k = Symbol('k', positive=True)
assert combsimp(
expand_mul(
integrate(log(x) * x**(k - 1) * exp(-x) / gamma(k),
(x, 0, oo)))) == polygamma(0, k)
def pdf(self, x):
k, l = self.k, self.l
return exp(-(x**2+l**2)/2)*x**k*l / (l*x)**(k/2) * besseli(k/2-1, l*x)
def test_mellin_transform_bessel():
from sympy import Max, Min, hyper, meijerg
MT = mellin_transform
# 8.4.19
assert MT(besselj(a, 2*sqrt(x)), x, s) == \
(gamma(a/2 + s)/gamma(a/2 - s + 1), (-re(a)/2, S(3)/4), True)
assert MT(sin(sqrt(x))*besselj(a, sqrt(x)), x, s) == \
(2**a*gamma(S(1)/2 - 2*s)*gamma((a+1)/2 + s) \
/ (gamma(1 - s- a/2)*gamma(1 + a - 2*s)),
(-(re(a) + 1)/2, S(1)/4), True)
# TODO why does this 2**(a+2)/4 not cancel?
assert MT(cos(sqrt(x))*besselj(a, sqrt(x)), x, s) == \
(2**(a+2)*gamma(a/2 + s)*gamma(S(1)/2 - 2*s)
/ (gamma(S(1)/2 - s - a/2)*gamma(a - 2*s + 1)) / 4,
(-re(a)/2, S(1)/4), True)
assert MT(besselj(a, sqrt(x))**2, x, s) == \
(gamma(a + s)*gamma(S(1)/2 - s)
/ (sqrt(pi)*gamma(1 - s)*gamma(1 + a - s)),
(-re(a), S(1)/2), True)
assert MT(besselj(a, sqrt(x))*besselj(-a, sqrt(x)), x, s) == \
(gamma(s)*gamma(S(1)/2 - s)
/ (sqrt(pi)*gamma(1 - a - s)*gamma(1 + a - s)),
(0, S(1)/2), True)
# NOTE: prudnikov gives the strip below as (1/2 - re(a), 1). As far as
# I can see this is wrong (since besselj(z) ~ 1/sqrt(z) for z large)
assert MT(besselj(a - 1, sqrt(x))*besselj(a, sqrt(x)), x, s) == \
(gamma(1-s)*gamma(a + s - S(1)/2)
/ (sqrt(pi)*gamma(S(3)/2 - s)*gamma(a - s + S(1)/2)),
(S(1)/2 - re(a), S(1)/2), True)
assert MT(besselj(a, sqrt(x))*besselj(b, sqrt(x)), x, s) == \
(2**(2*s)*gamma(1 - 2*s)*gamma((a+b)/2 + s)
/ (gamma(1 - s + (b-a)/2)*gamma(1 - s + (a-b)/2)
*gamma( 1 - s + (a+b)/2)),
(-(re(a) + re(b))/2, S(1)/2), True)
assert MT(besselj(a, sqrt(x))**2 + besselj(-a, sqrt(x))**2, x, s)[1:] == \
((Max(re(a), -re(a)), S(1)/2), True)
# Section 8.4.20
assert MT(bessely(a, 2*sqrt(x)), x, s) == \
(-cos(pi*a/2 - pi*s)*gamma(s - a/2)*gamma(s + a/2)/pi,
(Max(-re(a)/2, re(a)/2), S(3)/4), True)
assert MT(sin(sqrt(x))*bessely(a, sqrt(x)), x, s) == \
(-2**(2*s)*sin(pi*a/2 - pi*s)*gamma(S(1)/2 - 2*s)
* gamma((1-a)/2 + s)*gamma((1+a)/2 + s)
/ (sqrt(pi)*gamma(1 - s - a/2)*gamma(1 - s + a/2)),
(Max(-(re(a) + 1)/2, (re(a) - 1)/2), S(1)/4), True)
assert MT(cos(sqrt(x))*bessely(a, sqrt(x)), x, s) == \
(-2**(2*s)*cos(pi*a/2 - pi*s)*gamma(s - a/2)*gamma(s + a/2)*gamma(S(1)/2 - 2*s)
/ (sqrt(pi)*gamma(S(1)/2 - s - a/2)*gamma(S(1)/2 - s + a/2)),
(Max(-re(a)/2, re(a)/2), S(1)/4), True)
assert MT(besselj(a, sqrt(x))*bessely(a, sqrt(x)), x, s) == \
(-cos(pi*s)*gamma(s)*gamma(a + s)*gamma(S(1)/2 - s)
/ (pi**S('3/2')*gamma(1 + a - s)),
(Max(-re(a), 0), S(1)/2), True)
assert MT(besselj(a, sqrt(x))*bessely(b, sqrt(x)), x, s) == \
(-2**(2*s)*cos(pi*a/2 - pi*b/2 + pi*s)*gamma(1 - 2*s)
* gamma(a/2 - b/2 + s)*gamma(a/2 + b/2 + s)
/ (pi*gamma(a/2 - b/2 - s + 1)*gamma(a/2 + b/2 - s + 1)),
(Max((-re(a) + re(b))/2, (-re(a) - re(b))/2), S(1)/2), True)
# NOTE bessely(a, sqrt(x))**2 and bessely(a, sqrt(x))*bessely(b, sqrt(x))
# are a mess (no matter what way you look at it ...)
assert MT(bessely(a, sqrt(x))**2, x, s)[1:] == \
((Max(-re(a), 0, re(a)), S(1)/2), True)
# Section 8.4.22
# TODO we can't do any of these (delicate cancellation)
# Section 8.4.23
assert MT(besselk(a, 2*sqrt(x)), x, s) == \
(gamma(s - a/2)*gamma(s + a/2)/2, (Max(-re(a)/2, re(a)/2), oo), True)
assert MT(besselj(a, 2*sqrt(2*sqrt(x)))*besselk(a, 2*sqrt(2*sqrt(x))), x, s) == \
(4**(-s)*gamma(2*s)*gamma(a/2 + s)/gamma(a/2 - s + 1)/2,
(Max(-re(a)/2, 0), oo), True)
# TODO bessely(a, x)*besselk(a, x) is a mess
assert MT(besseli(a, sqrt(x))*besselk(a, sqrt(x)), x, s) == \
(gamma(s)*gamma(a + s)*gamma(-s + S(1)/2)/(2*sqrt(pi)*gamma(a - s + 1)),
(Max(-re(a), 0), S(1)/2), True)
assert MT(besseli(b, sqrt(x))*besselk(a, sqrt(x)), x, s) == \
(2**(2*s - 1)*gamma(-2*s + 1)*gamma(-a/2 + b/2 + s)*gamma(a/2 + b/2 + s) \
/(gamma(-a/2 + b/2 - s + 1)*gamma(a/2 + b/2 - s + 1)),
(Max(-re(a)/2 - re(b)/2, re(a)/2 - re(b)/2), S(1)/2), True)
# TODO products of besselk are a mess
# TODO this can be simplified considerably (although I have no idea how)
mt = MT(exp(-x/2)*besselk(a, x/2), x, s)
assert not mt[0].has(meijerg, hyper)
assert mt[1:] == ((Max(-re(a), re(a)), oo), True)
def test_bessel():
from sympy import besselj, Heaviside, besseli, polar_lift, exp_polar
assert integrate(besselj(a, z) * besselj(b, z) / z, (z, 0, oo), meijerg=True, conds="none") == 2 * sin(
pi * a / 2 - pi * b / 2
) / (pi * (a - b) * (a + b))
assert integrate(besselj(a, z) * besselj(a, z) / z, (z, 0, oo), meijerg=True, conds="none") == 1 / (2 * a)
# TODO more orthogonality integrals
# TODO there is actually a lot to improve here, this example is a good
# stress-test
# (the original integral is not recognised, the convergence conditions are
# wrong, and the result can be simplified to besselj(y, z))
assert (
simplify(
integrate(
sin(z * x) * (x ** 2 - 1) ** (-(y + S(1) / 2)) * Heaviside(x ** 2 - 1),
(x, 0, oo),
meijerg=True,
conds="none",
)
* 2
/ ((z / 2) ** y * sqrt(pi) * gamma(S(1) / 2 - y))
)
== 2
* (z ** 2 / 4) ** (y + S(1) / 2)
* (z / 2) ** (-y)
* (2 * exp_polar(-I * pi / 2) / z) ** y
* besseli(y, z * exp_polar(I * pi / 2))
/ z
)
# Werner Rosenheinrich
# SOME INDEFINITE INTEGRALS OF BESSEL FUNCTIONS
assert integrate(x * besselj(0, x), x, meijerg=True) == x * besselj(1, x)
assert integrate(x * besseli(0, x), x, meijerg=True) == x * besseli(1, x)
# TODO can do higher powers, but come out as high order ... should they be
# reduced to order 0, 1?
assert integrate(besselj(1, x), x, meijerg=True) == -besselj(0, x)
assert integrate(besselj(1, x) ** 2 / x, x, meijerg=True) == -(besselj(0, x) ** 2 + besselj(1, x) ** 2) / 2
# TODO more besseli when tables are extended or recursive mellin works
assert (
integrate(besselj(0, x) ** 2 / x ** 2, x, meijerg=True)
== -2 * x * besselj(0, x) ** 2
- 2 * x * besselj(1, x) ** 2
+ 2 * besselj(0, x) * besselj(1, x)
- besselj(0, x) ** 2 / x
)
assert integrate(besselj(0, x) * besselj(1, x), x, meijerg=True) == -besselj(0, x) ** 2 / 2
assert integrate(x ** 2 * besselj(0, x) * besselj(1, x), x, meijerg=True) == x ** 2 * besselj(1, x) ** 2 / 2
assert integrate(besselj(0, x) * besselj(1, x) / x, x, meijerg=True) == x * besselj(0, x) ** 2 + x * besselj(
1, x
) ** 2 - besselj(0, x) * besselj(1, x)
# TODO how does besselj(0, a*x)*besselj(0, b*x) work?
# TODO how does besselj(0, x)**2*besselj(1, x)**2 work?
# TODO sin(x)*besselj(0, x) etc come out a mess
# TODO can x*log(x)*besselj(0, x) be done?
# TODO how does besselj(1, x)*besselj(0, x+a) work?
# TODO more indefinite integrals when struve functions etc are implemented
# test a substitution
assert integrate(besselj(1, x ** 2) * x, x, meijerg=True) == -besselj(0, x ** 2) / 2
def test_probability():
# various integrals from probability theory
from sympy.abc import x, y, z
from sympy import symbols, Symbol, Abs, expand_mul, combsimp, powsimp
mu1, mu2 = symbols('mu1 mu2', real=True, finite=True, bounded=True)
sigma1, sigma2 = symbols('sigma1 sigma2', real=True, finite=True,
bounded=True, positive=True)
rate = Symbol('lambda', real=True, positive=True, bounded=True)
def normal(x, mu, sigma):
return 1/sqrt(2*pi*sigma**2)*exp(-(x-mu)**2/2/sigma**2)
def exponential(x, rate):
return rate*exp(-rate*x)
assert integrate(normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) == 1
assert integrate(x*normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) == mu1
assert integrate(x**2*normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) \
== mu1**2 + sigma1**2
assert integrate(x**3*normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) \
== mu1**3 + 3*mu1*sigma1**2
assert integrate(normal(x, mu1, sigma1)*normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo), meijerg=True) == 1
assert integrate(x*normal(x, mu1, sigma1)*normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo), meijerg=True) == mu1
assert integrate(y*normal(x, mu1, sigma1)*normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo), meijerg=True) == mu2
assert integrate(x*y*normal(x, mu1, sigma1)*normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo), meijerg=True) == mu1*mu2
assert integrate((x+y+1)*normal(x, mu1, sigma1)*normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo), meijerg=True) == 1 + mu1 + mu2
assert integrate((x+y-1)*normal(x, mu1, sigma1)*normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo), meijerg=True) == -1 + mu1 + mu2
i = integrate(x**2*normal(x, mu1, sigma1)*normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo), meijerg=True)
assert not i.has(Abs)
assert simplify(i) == mu1**2 + sigma1**2
assert integrate(y**2*normal(x, mu1, sigma1)*normal(y, mu2, sigma2),
(x, -oo, oo), (y, -oo, oo), meijerg=True) == \
sigma2**2 + mu2**2
assert integrate(exponential(x, rate), (x, 0, oo), meijerg=True) == 1
assert integrate(x*exponential(x, rate), (x, 0, oo), meijerg=True) == 1/rate
assert integrate(x**2*exponential(x, rate), (x, 0, oo), meijerg=True) \
== 2/rate**2
def E(expr):
res1 = integrate(expr*exponential(x, rate)*normal(y, mu1, sigma1),
(x, 0, oo), (y, -oo, oo), meijerg=True)
res2 = integrate(expr*exponential(x, rate)*normal(y, mu1, sigma1),
(y, -oo, oo), (x, 0, oo), meijerg=True)
assert expand_mul(res1) == expand_mul(res2)
return res1
assert E(1) == 1
assert E(x*y) == mu1/rate
assert E(x*y**2) == mu1**2/rate + sigma1**2/rate
assert simplify(E((x+y+1)**2) - E(x+y+1)**2) == (rate**2*sigma1**2 + 1)/rate**2
assert simplify(E((x+y-1)**2) - E(x+y-1)**2) == (rate**2*sigma1**2 + 1)/rate**2
assert simplify(E((x+y)**2) - E(x+y)**2) == (rate**2*sigma1**2 + 1)/rate**2
# Beta' distribution
alpha, beta = symbols('alpha beta', positive=True)
betadist = x**(alpha-1)*(1+x)**(-alpha - beta)*gamma(alpha+beta) \
/gamma(alpha)/gamma(beta)
assert integrate(betadist, (x, 0, oo), meijerg=True) == 1
i = integrate(x*betadist, (x, 0, oo), meijerg=True, conds='separate')
assert (combsimp(i[0]), i[1]) == (alpha/(beta - 1), 1 < beta)
j = integrate(x**2*betadist, (x, 0, oo), meijerg=True, conds='separate')
assert j[1] == (1 < beta - 1)
assert combsimp(j[0] - i[0]**2) == (alpha + beta - 1)*alpha \
/(beta - 2)/(beta - 1)**2
# Chi distribution
k = Symbol('k', integer=True, positive=True)
chi = 2**(1-k/2)*x**(k-1)*exp(-x**2/2)/gamma(k/2)
assert powsimp(integrate(chi, (x, 0, oo), meijerg=True)) == 1
assert simplify(integrate(x*chi, (x, 0, oo), meijerg=True)) == \
sqrt(2)*gamma((k + 1)/2)/gamma(k/2)
assert simplify(integrate(x**2*chi, (x, 0, oo), meijerg=True)) == k
# Chi^2 distribution
chisquared = 2**(-k/2)/gamma(k/2)*x**(k/2-1)*exp(-x/2)
assert powsimp(integrate(chisquared, (x, 0, oo), meijerg=True)) == 1
assert simplify(integrate(x*chisquared, (x, 0, oo), meijerg=True)) == k
assert simplify(integrate(x**2*chisquared, (x, 0, oo), meijerg=True)) == \
k*(k + 2)
assert combsimp(integrate(((x-k)/sqrt(2*k))**3*chisquared, (x, 0, oo),
meijerg=True)) == 2*sqrt(2)/sqrt(k)
# Dagum distribution
a, b, p = symbols('a b p', positive=True)
# XXX (x/b)**a does not work
dagum = a*p/x*(x/b)**(a*p)/(1 + x**a/b**a)**(p+1)
assert simplify(integrate(dagum, (x, 0, oo), meijerg=True)) == 1
# XXX conditions are a mess
assert simplify(integrate(x*dagum, (x, 0, oo), meijerg=True, conds='none')) \
== b*gamma(1 - 1/a)*gamma(p + 1/a)/gamma(p)
assert simplify(integrate(x**2*dagum, (x, 0, oo), meijerg=True, conds='none')) \
== b**2*gamma(1 - 2/a)*gamma(p + 2/a)/gamma(p)
# F-distribution
d1, d2 = symbols('d1 d2', positive=True)
f = sqrt(((d1*x)**d1 * d2**d2)/(d1*x + d2)**(d1+d2))/x \
/gamma(d1/2)/gamma(d2/2)*gamma((d1 + d2)/2)
assert simplify(integrate(f, (x, 0, oo), meijerg=True)) == 1
# TODO conditions are a mess
assert simplify(integrate(x*f, (x, 0, oo), meijerg=True, conds='none')) == \
d2/(d2 - 2)
assert simplify(integrate(x**2*f, (x, 0, oo), meijerg=True, conds='none')) == \
d2**2*(d1 + 2)/d1/(d2 - 4)/(d2 - 2)
# TODO gamma, inverse gaussian, Levi, log-logistic, rayleigh, weibull
# rice distribution
from sympy import besseli
nu, sigma = symbols('nu sigma', positive=True)
rice = x/sigma**2*exp(-(x**2+ nu**2)/2/sigma**2)*besseli(0, x*nu/sigma**2)
assert integrate(rice, (x, 0, oo), meijerg=True) == 1
# can someone verify higher moments?
# Laplace distribution
mu = Symbol('mu', real=True)
b = Symbol('b', positive=True)
laplace = exp(-abs(x-mu)/b)/2/b
assert integrate(laplace, (x, -oo, oo), meijerg=True) == 1
assert integrate(x*laplace, (x, -oo, oo), meijerg=True) == mu
assert integrate(x**2*laplace, (x, -oo, oo), meijerg=True) == 2*b**2 + mu**2
# TODO are there other distributions supported on (-oo, oo) that we can do?
# misc tests
k = Symbol('k', integer=True)
assert combsimp(expand_mul(integrate(log(x) * x**(k-1) * exp(-x) / gamma(k),
(x, 0, oo), conds='none'))) == polygamma(0, k)
def test_expand():
from sympy import besselsimp, Symbol, exp, exp_polar, I
assert expand_func(besselj(S(1)/2, z).rewrite(jn)) == \
sqrt(2)*sin(z)/(sqrt(pi)*sqrt(z))
assert expand_func(bessely(S(1)/2, z).rewrite(yn)) == \
-sqrt(2)*cos(z)/(sqrt(pi)*sqrt(z))
# XXX: teach sin/cos to work around arguments like
# x*exp_polar(I*pi*n/2). Then change besselsimp -> expand_func
assert besselsimp(besseli(S(1)/2, z)) == sqrt(2)*sinh(z)/(sqrt(pi)*sqrt(z))
def check(eq, ans):
return tn(eq, ans) and eq == ans
rn = randcplx(a=1, b=0, d=0, c=2)
assert check(expand_func(besseli(rn, x)), \
besseli(rn - 2, x) - 2*(rn - 1)*besseli(rn - 1, x)/x)
assert check(expand_func(besseli(-rn, x)), \
besseli(-rn + 2, x) + 2*(-rn + 1)*besseli(-rn + 1, x)/x)
assert check(expand_func(besselj(rn, x)), \
-besselj(rn - 2, x) + 2*(rn - 1)*besselj(rn - 1, x)/x)
assert check(expand_func(besselj(-rn, x)), \
-besselj(-rn + 2, x) + 2*(-rn + 1)*besselj(-rn + 1, x)/x)
assert check(expand_func(besselk(rn, x)), \
besselk(rn - 2, x) + 2*(rn - 1)*besselk(rn - 1, x)/x)
assert check(expand_func(besselk(-rn, x)), \
besselk(-rn + 2, x) - 2*(-rn + 1)*besselk(-rn + 1, x)/x)
assert check(expand_func(bessely(rn, x)), \
-bessely(rn - 2, x) + 2*(rn - 1)*bessely(rn - 1, x)/x)
assert check(expand_func(bessely(-rn, x)), \
-bessely(-rn + 2, x) + 2*(-rn + 1)*bessely(-rn + 1, x)/x)
n = Symbol('n', integer=True, positive=True)
assert expand_func(besseli(n + 2, z)) == \
besseli(n, z) + (-2*n - 2)*(-2*n*besseli(n, z)/z + besseli(n - 1, z))/z
assert expand_func(besselj(n + 2, z)) == \
-besselj(n, z) + (2*n + 2)*(2*n*besselj(n, z)/z - besselj(n - 1, z))/z
assert expand_func(besselk(n + 2, z)) == \
besselk(n, z) + (2*n + 2)*(2*n*besselk(n, z)/z + besselk(n - 1, z))/z
assert expand_func(bessely(n + 2, z)) == \
-bessely(n, z) + (2*n + 2)*(2*n*bessely(n, z)/z - bessely(n - 1, z))/z
assert expand_func(besseli(n + S(1)/2, z).rewrite(jn)) == \
sqrt(2)*sqrt(z)*exp(-I*pi*(n + S(1)/2)/2)* \
exp_polar(I*pi/4)*jn(n, z*exp_polar(I*pi/2))/sqrt(pi)
assert expand_func(besselj(n + S(1)/2, z).rewrite(jn)) == \
sqrt(2)*sqrt(z)*jn(n, z)/sqrt(pi)
def test_expand():
from sympy import besselsimp, Symbol, exp, exp_polar, I
assert expand_func(besselj(S(1)/2, z).rewrite(jn)) == \
sqrt(2)*sin(z)/(sqrt(pi)*sqrt(z))
assert expand_func(bessely(S(1)/2, z).rewrite(yn)) == \
-sqrt(2)*cos(z)/(sqrt(pi)*sqrt(z))
# XXX: teach sin/cos to work around arguments like
# x*exp_polar(I*pi*n/2). Then change besselsimp -> expand_func
assert besselsimp(besselj(S(1)/2, z)) == sqrt(2)*sin(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besselj(S(-1)/2, z)) == sqrt(2)*cos(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besselj(S(5)/2, z)) == \
-sqrt(2)*(z**2*sin(z) + 3*z*cos(z) - 3*sin(z))/(sqrt(pi)*z**(S(5)/2))
assert besselsimp(besselj(-S(5)/2, z)) == \
-sqrt(2)*(z**2*cos(z) - 3*z*sin(z) - 3*cos(z))/(sqrt(pi)*z**(S(5)/2))
assert besselsimp(bessely(S(1)/2, z)) == \
-(sqrt(2)*cos(z))/(sqrt(pi)*sqrt(z))
assert besselsimp(bessely(S(-1)/2, z)) == sqrt(2)*sin(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(bessely(S(5)/2, z)) == \
sqrt(2)*(z**2*cos(z) - 3*z*sin(z) - 3*cos(z))/(sqrt(pi)*z**(S(5)/2))
assert besselsimp(bessely(S(-5)/2, z)) == \
-sqrt(2)*(z**2*sin(z) + 3*z*cos(z) - 3*sin(z))/(sqrt(pi)*z**(S(5)/2))
assert besselsimp(besseli(S(1)/2, z)) == sqrt(2)*sinh(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besseli(S(-1)/2, z)) == \
sqrt(2)*cosh(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besseli(S(5)/2, z)) == \
sqrt(2)*(z**2*sinh(z) - 3*z*cosh(z) + 3*sinh(z))/(sqrt(pi)*z**(S(5)/2))
assert besselsimp(besseli(S(-5)/2, z)) == \
sqrt(2)*(z**2*cosh(z) - 3*z*sinh(z) + 3*cosh(z))/(sqrt(pi)*z**(S(5)/2))
assert besselsimp(besselk(S(1)/2, z)) == \
besselsimp(besselk(S(-1)/2, z)) == sqrt(pi)*exp(-z)/(sqrt(2)*sqrt(z))
assert besselsimp(besselk(S(5)/2, z)) == \
besselsimp(besselk(S(-5)/2, z)) == \
sqrt(2)*sqrt(pi)*(z**2 + 3*z + 3)*exp(-z)/(2*z**(S(5)/2))
def check(eq, ans):
return tn(eq, ans) and eq == ans
rn = randcplx(a=1, b=0, d=0, c=2)
for besselx in [besselj, bessely, besseli, besselk]:
ri = S(2*randint(-11, 10) + 1) / 2 # half integer in [-21/2, 21/2]
assert tn(besselsimp(besselx(ri, z)), besselx(ri, z))
assert check(expand_func(besseli(rn, x)),
besseli(rn - 2, x) - 2*(rn - 1)*besseli(rn - 1, x)/x)
assert check(expand_func(besseli(-rn, x)),
besseli(-rn + 2, x) + 2*(-rn + 1)*besseli(-rn + 1, x)/x)
assert check(expand_func(besselj(rn, x)),
-besselj(rn - 2, x) + 2*(rn - 1)*besselj(rn - 1, x)/x)
assert check(expand_func(besselj(-rn, x)),
-besselj(-rn + 2, x) + 2*(-rn + 1)*besselj(-rn + 1, x)/x)
assert check(expand_func(besselk(rn, x)),
besselk(rn - 2, x) + 2*(rn - 1)*besselk(rn - 1, x)/x)
assert check(expand_func(besselk(-rn, x)),
besselk(-rn + 2, x) - 2*(-rn + 1)*besselk(-rn + 1, x)/x)
assert check(expand_func(bessely(rn, x)),
-bessely(rn - 2, x) + 2*(rn - 1)*bessely(rn - 1, x)/x)
assert check(expand_func(bessely(-rn, x)),
-bessely(-rn + 2, x) + 2*(-rn + 1)*bessely(-rn + 1, x)/x)
n = Symbol('n', integer=True, positive=True)
assert expand_func(besseli(n + 2, z)) == \
besseli(n, z) + (-2*n - 2)*(-2*n*besseli(n, z)/z + besseli(n - 1, z))/z
assert expand_func(besselj(n + 2, z)) == \
-besselj(n, z) + (2*n + 2)*(2*n*besselj(n, z)/z - besselj(n - 1, z))/z
assert expand_func(besselk(n + 2, z)) == \
besselk(n, z) + (2*n + 2)*(2*n*besselk(n, z)/z + besselk(n - 1, z))/z
assert expand_func(bessely(n + 2, z)) == \
-bessely(n, z) + (2*n + 2)*(2*n*bessely(n, z)/z - bessely(n - 1, z))/z
assert expand_func(besseli(n + S(1)/2, z).rewrite(jn)) == \
(sqrt(2)*sqrt(z)*exp(-I*pi*(n + S(1)/2)/2) *
exp_polar(I*pi/4)*jn(n, z*exp_polar(I*pi/2))/sqrt(pi))
assert expand_func(besselj(n + S(1)/2, z).rewrite(jn)) == \
sqrt(2)*sqrt(z)*jn(n, z)/sqrt(pi)
r = Symbol('r', real=True)
p = Symbol('p', positive=True)
i = Symbol('i', integer=True)
for besselx in [besselj, bessely, besseli, besselk]:
assert besselx(i, p).is_real
assert besselx(i, x).is_real is None
assert besselx(x, z).is_real is None
for besselx in [besselj, besseli]:
assert besselx(i, r).is_real
for besselx in [bessely, besselk]:
assert besselx(i, r).is_real is None
def hopkins(u):
return sm.besseli(1,x) * sm.exp(-(x/2)**2 / L)
def test_von_mises():
mu = Symbol("mu")
k = Symbol("k", positive=True)
X = VonMises("x", mu, k)
assert density(X)(x) == exp(k*cos(x - mu))/(2*pi*besseli(0, k))
def test_mellin_transform_bessel():
from sympy import Max, Min, hyper, meijerg
MT = mellin_transform
# 8.4.19
assert MT(besselj(a, 2*sqrt(x)), x, s) == \
(gamma(a/2 + s)/gamma(a/2 - s + 1), (-re(a)/2, S(3)/4), True)
assert MT(sin(sqrt(x))*besselj(a, sqrt(x)), x, s) == \
(2**a*gamma(-2*s + S(1)/2)*gamma(a/2 + s + S(1)/2)/(
gamma(-a/2 - s + 1)*gamma(a - 2*s + 1)), (
-re(a)/2 - S(1)/2, S(1)/4), True)
assert MT(cos(sqrt(x))*besselj(a, sqrt(x)), x, s) == \
(2**a*gamma(a/2 + s)*gamma(-2*s + S(1)/2)/(
gamma(-a/2 - s + S(1)/2)*gamma(a - 2*s + 1)), (
-re(a)/2, S(1)/4), True)
assert MT(besselj(a, sqrt(x))**2, x, s) == \
(gamma(a + s)*gamma(S(1)/2 - s)
/ (sqrt(pi)*gamma(1 - s)*gamma(1 + a - s)),
(-re(a), S(1)/2), True)
assert MT(besselj(a, sqrt(x))*besselj(-a, sqrt(x)), x, s) == \
(gamma(s)*gamma(S(1)/2 - s)
/ (sqrt(pi)*gamma(1 - a - s)*gamma(1 + a - s)),
(0, S(1)/2), True)
# NOTE: prudnikov gives the strip below as (1/2 - re(a), 1). As far as
# I can see this is wrong (since besselj(z) ~ 1/sqrt(z) for z large)
assert MT(besselj(a - 1, sqrt(x))*besselj(a, sqrt(x)), x, s) == \
(gamma(1 - s)*gamma(a + s - S(1)/2)
/ (sqrt(pi)*gamma(S(3)/2 - s)*gamma(a - s + S(1)/2)),
(S(1)/2 - re(a), S(1)/2), True)
assert MT(besselj(a, sqrt(x))*besselj(b, sqrt(x)), x, s) == \
(4**s*gamma(1 - 2*s)*gamma((a + b)/2 + s)
/ (gamma(1 - s + (b - a)/2)*gamma(1 - s + (a - b)/2)
*gamma( 1 - s + (a + b)/2)),
(-(re(a) + re(b))/2, S(1)/2), True)
assert MT(besselj(a, sqrt(x))**2 + besselj(-a, sqrt(x))**2, x, s)[1:] == \
((Max(re(a), -re(a)), S(1)/2), True)
# Section 8.4.20
assert MT(bessely(a, 2*sqrt(x)), x, s) == \
(-cos(pi*(a/2 - s))*gamma(s - a/2)*gamma(s + a/2)/pi,
(Max(-re(a)/2, re(a)/2), S(3)/4), True)
assert MT(sin(sqrt(x))*bessely(a, sqrt(x)), x, s) == \
(-4**s*sin(pi*(a/2 - s))*gamma(S(1)/2 - 2*s)
* gamma((1 - a)/2 + s)*gamma((1 + a)/2 + s)
/ (sqrt(pi)*gamma(1 - s - a/2)*gamma(1 - s + a/2)),
(Max(-(re(a) + 1)/2, (re(a) - 1)/2), S(1)/4), True)
assert MT(cos(sqrt(x))*bessely(a, sqrt(x)), x, s) == \
(-4**s*cos(pi*(a/2 - s))*gamma(s - a/2)*gamma(s + a/2)*gamma(S(1)/2 - 2*s)
/ (sqrt(pi)*gamma(S(1)/2 - s - a/2)*gamma(S(1)/2 - s + a/2)),
(Max(-re(a)/2, re(a)/2), S(1)/4), True)
assert MT(besselj(a, sqrt(x))*bessely(a, sqrt(x)), x, s) == \
(-cos(pi*s)*gamma(s)*gamma(a + s)*gamma(S(1)/2 - s)
/ (pi**S('3/2')*gamma(1 + a - s)),
(Max(-re(a), 0), S(1)/2), True)
assert MT(besselj(a, sqrt(x))*bessely(b, sqrt(x)), x, s) == \
(-4**s*cos(pi*(a/2 - b/2 + s))*gamma(1 - 2*s)
* gamma(a/2 - b/2 + s)*gamma(a/2 + b/2 + s)
/ (pi*gamma(a/2 - b/2 - s + 1)*gamma(a/2 + b/2 - s + 1)),
(Max((-re(a) + re(b))/2, (-re(a) - re(b))/2), S(1)/2), True)
# NOTE bessely(a, sqrt(x))**2 and bessely(a, sqrt(x))*bessely(b, sqrt(x))
# are a mess (no matter what way you look at it ...)
assert MT(bessely(a, sqrt(x))**2, x, s)[1:] == \
((Max(-re(a), 0, re(a)), S(1)/2), True)
# Section 8.4.22
# TODO we can't do any of these (delicate cancellation)
# Section 8.4.23
assert MT(besselk(a, 2*sqrt(x)), x, s) == \
(gamma(
s - a/2)*gamma(s + a/2)/2, (Max(-re(a)/2, re(a)/2), oo), True)
assert MT(besselj(a, 2*sqrt(2*sqrt(x)))*besselk(
a, 2*sqrt(2*sqrt(x))), x, s) == (4**(-s)*gamma(2*s)*
gamma(a/2 + s)/(2*gamma(a/2 - s + 1)), (Max(0, -re(a)/2), oo), True)
# TODO bessely(a, x)*besselk(a, x) is a mess
assert MT(besseli(a, sqrt(x))*besselk(a, sqrt(x)), x, s) == \
(gamma(s)*gamma(
a + s)*gamma(-s + S(1)/2)/(2*sqrt(pi)*gamma(a - s + 1)),
(Max(-re(a), 0), S(1)/2), True)
assert MT(besseli(b, sqrt(x))*besselk(a, sqrt(x)), x, s) == \
(2**(2*s - 1)*gamma(-2*s + 1)*gamma(-a/2 + b/2 + s)* \
gamma(a/2 + b/2 + s)/(gamma(-a/2 + b/2 - s + 1)* \
gamma(a/2 + b/2 - s + 1)), (Max(-re(a)/2 - re(b)/2, \
re(a)/2 - re(b)/2), S(1)/2), True)
# TODO products of besselk are a mess
mt = MT(exp(-x/2)*besselk(a, x/2), x, s)
mt0 = combsimp((trigsimp(combsimp(mt[0].expand(func=True)))))
assert mt0 == 2*pi**(S(3)/2)*cos(pi*s)*gamma(-s + S(1)/2)/(
(cos(2*pi*a) - cos(2*pi*s))*gamma(-a - s + 1)*gamma(a - s + 1))
assert mt[1:] == ((Max(-re(a), re(a)), oo), True)
def test_probability():
# various integrals from probability theory
from sympy.abc import x, y
from sympy import symbols, Symbol, Abs, expand_mul, combsimp, powsimp, sin
mu1, mu2 = symbols("mu1 mu2", real=True, nonzero=True, finite=True)
sigma1, sigma2 = symbols("sigma1 sigma2", real=True, nonzero=True, finite=True, positive=True)
rate = Symbol("lambda", real=True, positive=True, finite=True)
def normal(x, mu, sigma):
return 1 / sqrt(2 * pi * sigma ** 2) * exp(-(x - mu) ** 2 / 2 / sigma ** 2)
def exponential(x, rate):
return rate * exp(-rate * x)
assert integrate(normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) == 1
assert integrate(x * normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) == mu1
assert integrate(x ** 2 * normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) == mu1 ** 2 + sigma1 ** 2
assert integrate(x ** 3 * normal(x, mu1, sigma1), (x, -oo, oo), meijerg=True) == mu1 ** 3 + 3 * mu1 * sigma1 ** 2
assert integrate(normal(x, mu1, sigma1) * normal(y, mu2, sigma2), (x, -oo, oo), (y, -oo, oo), meijerg=True) == 1
assert (
integrate(x * normal(x, mu1, sigma1) * normal(y, mu2, sigma2), (x, -oo, oo), (y, -oo, oo), meijerg=True) == mu1
)
assert (
integrate(y * normal(x, mu1, sigma1) * normal(y, mu2, sigma2), (x, -oo, oo), (y, -oo, oo), meijerg=True) == mu2
)
assert (
integrate(x * y * normal(x, mu1, sigma1) * normal(y, mu2, sigma2), (x, -oo, oo), (y, -oo, oo), meijerg=True)
== mu1 * mu2
)
assert (
integrate(
(x + y + 1) * normal(x, mu1, sigma1) * normal(y, mu2, sigma2), (x, -oo, oo), (y, -oo, oo), meijerg=True
)
== 1 + mu1 + mu2
)
assert (
integrate(
(x + y - 1) * normal(x, mu1, sigma1) * normal(y, mu2, sigma2), (x, -oo, oo), (y, -oo, oo), meijerg=True
)
== -1 + mu1 + mu2
)
i = integrate(x ** 2 * normal(x, mu1, sigma1) * normal(y, mu2, sigma2), (x, -oo, oo), (y, -oo, oo), meijerg=True)
assert not i.has(Abs)
assert simplify(i) == mu1 ** 2 + sigma1 ** 2
assert (
integrate(y ** 2 * normal(x, mu1, sigma1) * normal(y, mu2, sigma2), (x, -oo, oo), (y, -oo, oo), meijerg=True)
== sigma2 ** 2 + mu2 ** 2
)
assert integrate(exponential(x, rate), (x, 0, oo), meijerg=True) == 1
assert integrate(x * exponential(x, rate), (x, 0, oo), meijerg=True) == 1 / rate
assert integrate(x ** 2 * exponential(x, rate), (x, 0, oo), meijerg=True) == 2 / rate ** 2
def E(expr):
res1 = integrate(expr * exponential(x, rate) * normal(y, mu1, sigma1), (x, 0, oo), (y, -oo, oo), meijerg=True)
res2 = integrate(expr * exponential(x, rate) * normal(y, mu1, sigma1), (y, -oo, oo), (x, 0, oo), meijerg=True)
assert expand_mul(res1) == expand_mul(res2)
return res1
assert E(1) == 1
assert E(x * y) == mu1 / rate
assert E(x * y ** 2) == mu1 ** 2 / rate + sigma1 ** 2 / rate
ans = sigma1 ** 2 + 1 / rate ** 2
assert simplify(E((x + y + 1) ** 2) - E(x + y + 1) ** 2) == ans
assert simplify(E((x + y - 1) ** 2) - E(x + y - 1) ** 2) == ans
assert simplify(E((x + y) ** 2) - E(x + y) ** 2) == ans
# Beta' distribution
alpha, beta = symbols("alpha beta", positive=True)
betadist = x ** (alpha - 1) * (1 + x) ** (-alpha - beta) * gamma(alpha + beta) / gamma(alpha) / gamma(beta)
assert integrate(betadist, (x, 0, oo), meijerg=True) == 1
i = integrate(x * betadist, (x, 0, oo), meijerg=True, conds="separate")
assert (combsimp(i[0]), i[1]) == (alpha / (beta - 1), 1 < beta)
j = integrate(x ** 2 * betadist, (x, 0, oo), meijerg=True, conds="separate")
assert j[1] == (1 < beta - 1)
assert combsimp(j[0] - i[0] ** 2) == (alpha + beta - 1) * alpha / (beta - 2) / (beta - 1) ** 2
# Beta distribution
# NOTE: this is evaluated using antiderivatives. It also tests that
# meijerint_indefinite returns the simplest possible answer.
a, b = symbols("a b", positive=True)
betadist = x ** (a - 1) * (-x + 1) ** (b - 1) * gamma(a + b) / (gamma(a) * gamma(b))
assert simplify(integrate(betadist, (x, 0, 1), meijerg=True)) == 1
assert simplify(integrate(x * betadist, (x, 0, 1), meijerg=True)) == a / (a + b)
assert simplify(integrate(x ** 2 * betadist, (x, 0, 1), meijerg=True)) == a * (a + 1) / (a + b) / (a + b + 1)
assert simplify(integrate(x ** y * betadist, (x, 0, 1), meijerg=True)) == gamma(a + b) * gamma(a + y) / gamma(
a
) / gamma(a + b + y)
# Chi distribution
k = Symbol("k", integer=True, positive=True)
chi = 2 ** (1 - k / 2) * x ** (k - 1) * exp(-x ** 2 / 2) / gamma(k / 2)
assert powsimp(integrate(chi, (x, 0, oo), meijerg=True)) == 1
assert simplify(integrate(x * chi, (x, 0, oo), meijerg=True)) == sqrt(2) * gamma((k + 1) / 2) / gamma(k / 2)
assert simplify(integrate(x ** 2 * chi, (x, 0, oo), meijerg=True)) == k
# Chi^2 distribution
chisquared = 2 ** (-k / 2) / gamma(k / 2) * x ** (k / 2 - 1) * exp(-x / 2)
assert powsimp(integrate(chisquared, (x, 0, oo), meijerg=True)) == 1
assert simplify(integrate(x * chisquared, (x, 0, oo), meijerg=True)) == k
assert simplify(integrate(x ** 2 * chisquared, (x, 0, oo), meijerg=True)) == k * (k + 2)
assert combsimp(integrate(((x - k) / sqrt(2 * k)) ** 3 * chisquared, (x, 0, oo), meijerg=True)) == 2 * sqrt(
2
) / sqrt(k)
# Dagum distribution
a, b, p = symbols("a b p", positive=True)
# XXX (x/b)**a does not work
dagum = a * p / x * (x / b) ** (a * p) / (1 + x ** a / b ** a) ** (p + 1)
assert simplify(integrate(dagum, (x, 0, oo), meijerg=True)) == 1
# XXX conditions are a mess
arg = x * dagum
assert simplify(integrate(arg, (x, 0, oo), meijerg=True, conds="none")) == a * b * gamma(1 - 1 / a) * gamma(
p + 1 + 1 / a
) / ((a * p + 1) * gamma(p))
assert simplify(integrate(x * arg, (x, 0, oo), meijerg=True, conds="none")) == a * b ** 2 * gamma(
1 - 2 / a
) * gamma(p + 1 + 2 / a) / ((a * p + 2) * gamma(p))
# F-distribution
d1, d2 = symbols("d1 d2", positive=True)
f = (
sqrt(((d1 * x) ** d1 * d2 ** d2) / (d1 * x + d2) ** (d1 + d2))
/ x
/ gamma(d1 / 2)
/ gamma(d2 / 2)
* gamma((d1 + d2) / 2)
)
assert simplify(integrate(f, (x, 0, oo), meijerg=True)) == 1
# TODO conditions are a mess
assert simplify(integrate(x * f, (x, 0, oo), meijerg=True, conds="none")) == d2 / (d2 - 2)
assert simplify(integrate(x ** 2 * f, (x, 0, oo), meijerg=True, conds="none")) == d2 ** 2 * (d1 + 2) / d1 / (
d2 - 4
) / (d2 - 2)
# TODO gamma, rayleigh
# inverse gaussian
lamda, mu = symbols("lamda mu", positive=True)
dist = sqrt(lamda / 2 / pi) * x ** (-S(3) / 2) * exp(-lamda * (x - mu) ** 2 / x / 2 / mu ** 2)
mysimp = lambda expr: simplify(expr.rewrite(exp))
assert mysimp(integrate(dist, (x, 0, oo))) == 1
assert mysimp(integrate(x * dist, (x, 0, oo))) == mu
assert mysimp(integrate((x - mu) ** 2 * dist, (x, 0, oo))) == mu ** 3 / lamda
assert mysimp(integrate((x - mu) ** 3 * dist, (x, 0, oo))) == 3 * mu ** 5 / lamda ** 2
# Levi
c = Symbol("c", positive=True)
assert integrate(sqrt(c / 2 / pi) * exp(-c / 2 / (x - mu)) / (x - mu) ** S("3/2"), (x, mu, oo)) == 1
# higher moments oo
# log-logistic
distn = (beta / alpha) * x ** (beta - 1) / alpha ** (beta - 1) / (1 + x ** beta / alpha ** beta) ** 2
assert simplify(integrate(distn, (x, 0, oo))) == 1
# NOTE the conditions are a mess, but correctly state beta > 1
assert simplify(integrate(x * distn, (x, 0, oo), conds="none")) == pi * alpha / beta / sin(pi / beta)
# (similar comment for conditions applies)
assert simplify(integrate(x ** y * distn, (x, 0, oo), conds="none")) == pi * alpha ** y * y / beta / sin(
pi * y / beta
)
# weibull
k = Symbol("k", positive=True)
n = Symbol("n", positive=True)
distn = k / lamda * (x / lamda) ** (k - 1) * exp(-(x / lamda) ** k)
assert simplify(integrate(distn, (x, 0, oo))) == 1
assert simplify(integrate(x ** n * distn, (x, 0, oo))) == lamda ** n * gamma(1 + n / k)
# rice distribution
from sympy import besseli
nu, sigma = symbols("nu sigma", positive=True)
rice = x / sigma ** 2 * exp(-(x ** 2 + nu ** 2) / 2 / sigma ** 2) * besseli(0, x * nu / sigma ** 2)
assert integrate(rice, (x, 0, oo), meijerg=True) == 1
# can someone verify higher moments?
# Laplace distribution
mu = Symbol("mu", real=True)
b = Symbol("b", positive=True)
laplace = exp(-abs(x - mu) / b) / 2 / b
assert integrate(laplace, (x, -oo, oo), meijerg=True) == 1
assert integrate(x * laplace, (x, -oo, oo), meijerg=True) == mu
assert integrate(x ** 2 * laplace, (x, -oo, oo), meijerg=True) == 2 * b ** 2 + mu ** 2
# TODO are there other distributions supported on (-oo, oo) that we can do?
# misc tests
k = Symbol("k", positive=True)
assert combsimp(expand_mul(integrate(log(x) * x ** (k - 1) * exp(-x) / gamma(k), (x, 0, oo)))) == polygamma(0, k)
