def test_airybi():
z = Symbol('z', extended_real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airybi(z), airybi)
assert airybi(0) == 3**Rational(5, 6) / (3 * gamma(Rational(2, 3)))
assert airybi(oo) == oo
assert airybi(-oo) == 0
assert diff(airybi(z), z) == airybiprime(z)
assert series(airybi(z), z, 0,
3) == (cbrt(3) * gamma(Rational(1, 3)) / (2 * pi) +
3**Rational(2, 3) * z * gamma(Rational(2, 3)) /
(2 * pi) + O(z**3))
l = Limit(
airybi(I / x) /
(exp(Rational(2, 3) *
(I / x)**Rational(3, 2)) * sqrt(pi * sqrt(I / x))), x, 0)
assert l.doit() == l
assert airybi(z).rewrite(hyper) == (root(3, 6) * z * hyper(
(), (Rational(4, 3), ), z**3 / 9) / gamma(Rational(1, 3)) +
3**Rational(5, 6) * hyper(
(), (Rational(2, 3), ), z**3 / 9) /
(3 * gamma(Rational(2, 3))))
assert isinstance(airybi(z).rewrite(besselj), airybi)
assert (airybi(t).rewrite(besselj) == sqrt(3) * sqrt(-t) *
(besselj(-1 / 3, 2 * (-t)**Rational(3, 2) / 3) -
besselj(Rational(1, 3), 2 * (-t)**Rational(3, 2) / 3)) / 3)
assert airybi(z).rewrite(besseli) == (
sqrt(3) * (z * besseli(Rational(1, 3), 2 * z**Rational(3, 2) / 3) /
cbrt(z**Rational(3, 2)) + cbrt(z**Rational(3, 2)) *
besseli(-Rational(1, 3), 2 * z**Rational(3, 2) / 3)) / 3)
assert airybi(p).rewrite(besseli) == (
sqrt(3) * sqrt(p) *
(besseli(-Rational(1, 3), 2 * p**Rational(3, 2) / 3) +
besseli(Rational(1, 3), 2 * p**Rational(3, 2) / 3)) / 3)
assert airybi(p).rewrite(besselj) == airybi(p)
assert expand_func(airybi(
2 *
cbrt(3 * z**5))) == (sqrt(3) * (1 - cbrt(z**5) / z**Rational(5, 3)) *
airyai(2 * cbrt(3) * z**Rational(5, 3)) / 2 +
(1 + cbrt(z**5) / z**Rational(5, 3)) *
airybi(2 * cbrt(3) * z**Rational(5, 3)) / 2)
assert expand_func(airybi(x * y)) == airybi(x * y)
assert expand_func(airybi(log(x))) == airybi(log(x))
assert expand_func(airybi(2 * root(3 * z**5, 5))) == airybi(
2 * root(3 * z**5, 5))
assert airybi(x).taylor_term(-1, x) == 0
def test_airyai():
z = Symbol('z', extended_real=False)
r = Symbol('r', extended_real=True)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airyai(z), airyai)
assert airyai(0) == cbrt(3)/(3*gamma(Rational(2, 3)))
assert airyai(oo) == 0
assert airyai(-oo) == 0
assert diff(airyai(z), z) == airyaiprime(z)
assert airyai(z).series(z, 0, 3) == (
3**Rational(5, 6)*gamma(Rational(1, 3))/(6*pi) - root(3, 6)*z*gamma(Rational(2, 3))/(2*pi) + O(z**3))
l = Limit(airyai(I/x)/(exp(-Rational(2, 3)*(I/x)**Rational(3, 2))*sqrt(pi*sqrt(I/x))/2), x, 0)
assert l.doit() == l # cover _airyais._eval_aseries
assert airyai(z).rewrite(hyper) == (
-3**Rational(2, 3)*z*hyper((), (Rational(4, 3),), z**3/9)/(3*gamma(Rational(1, 3))) +
cbrt(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*cbrt(z**Rational(3, 2))) +
cbrt(z**Rational(3, 2))*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*cbrt(3*z**5))) == (
-sqrt(3)*(-1 + cbrt(z**5)/z**Rational(5, 3))*airybi(2*cbrt(3)*z**Rational(5, 3))/6 +
(1 + cbrt(z**5)/z**Rational(5, 3))*airyai(2*cbrt(3)*z**Rational(5, 3))/2)
assert expand_func(airyai(x*y)) == airyai(x*y)
assert expand_func(airyai(log(x))) == airyai(log(x))
assert expand_func(airyai(2*root(3*z**5, 5))) == airyai(2*root(3*z**5, 5))
assert (airyai(r).as_real_imag() ==
airyai(r).as_real_imag(deep=False) == (airyai(r), 0))
assert airyai(x).as_real_imag() == airyai(x).as_real_imag(deep=False)
assert (airyai(x).as_real_imag() ==
(airyai(re(x) - I*re(x)*abs(im(x))/abs(re(x)))/2 +
airyai(re(x) + I*re(x)*abs(im(x))/abs(re(x)))/2,
I*(airyai(re(x) - I*re(x)*abs(im(x))/abs(re(x))) -
airyai(re(x) + I*re(x)*abs(im(x))/abs(re(x)))) *
re(x)*abs(im(x))/(2*im(x)*abs(re(x)))))
assert airyai(x).taylor_term(-1, x) == 0
def test_airyai():
z = Symbol('z', extended_real=False)
r = Symbol('r', extended_real=True)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airyai(z), airyai)
assert airyai(0) == cbrt(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) - root(3, 6)*z*gamma(Rational(2, 3))/(2*pi) + O(z**3))
l = Limit(airyai(I/x)/(exp(-Rational(2, 3)*(I/x)**Rational(3, 2))*sqrt(pi*sqrt(I/x))/2), x, 0)
assert l.doit() == l # cover _airyais._eval_aseries
assert airyai(z).rewrite(hyper) == (
-3**Rational(2, 3)*z*hyper((), (Rational(4, 3),), z**3/9)/(3*gamma(Rational(1, 3))) +
cbrt(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*cbrt(z**Rational(3, 2))) +
cbrt(z**Rational(3, 2))*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*cbrt(3*z**5))) == (
-sqrt(3)*(-1 + cbrt(z**5)/z**Rational(5, 3))*airybi(2*cbrt(3)*z**Rational(5, 3))/6 +
(1 + cbrt(z**5)/z**Rational(5, 3))*airyai(2*cbrt(3)*z**Rational(5, 3))/2)
assert expand_func(airyai(x*y)) == airyai(x*y)
assert expand_func(airyai(log(x))) == airyai(log(x))
assert expand_func(airyai(2*root(3*z**5, 5))) == airyai(2*root(3*z**5, 5))
assert (airyai(r).as_real_imag() ==
airyai(r).as_real_imag(deep=False) == (airyai(r), 0))
assert airyai(x).as_real_imag() == airyai(x).as_real_imag(deep=False)
assert (airyai(x).as_real_imag() ==
(airyai(re(x) - I*re(x)*abs(im(x))/abs(re(x)))/2 +
airyai(re(x) + I*re(x)*abs(im(x))/abs(re(x)))/2,
I*(airyai(re(x) - I*re(x)*abs(im(x))/abs(re(x))) -
airyai(re(x) + I*re(x)*abs(im(x))/Abs(re(x)))) *
re(x)*abs(im(x))/(2*im(x)*abs(re(x)))))
assert airyai(x).taylor_term(-1, x) == 0
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_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
pytest.raises(ArgumentIndexError, lambda: besselj(n, z).fdiff(3))
pytest.raises(ArgumentIndexError, lambda: jn(n, z).fdiff(3))
pytest.raises(ArgumentIndexError, lambda: airyai(z).fdiff(2))
pytest.raises(ArgumentIndexError, lambda: airybi(z).fdiff(2))
pytest.raises(ArgumentIndexError, lambda: airyaiprime(z).fdiff(2))
pytest.raises(ArgumentIndexError, lambda: airybiprime(z).fdiff(2))
def test_branching():
from diofant 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_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):
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 - expr2).evalf(strict=False) < 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_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
pytest.raises(ArgumentIndexError, lambda: besselj(n, z).fdiff(3))
pytest.raises(ArgumentIndexError, lambda: jn(n, z).fdiff(3))
pytest.raises(ArgumentIndexError, lambda: airyai(z).fdiff(2))
pytest.raises(ArgumentIndexError, lambda: airybi(z).fdiff(2))
pytest.raises(ArgumentIndexError, lambda: airyaiprime(z).fdiff(2))
pytest.raises(ArgumentIndexError, lambda: airybiprime(z).fdiff(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):
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 - expr2).evalf(strict=False) < 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_airybiprime():
z = Symbol('z', extended_real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airybiprime(z), airybiprime)
assert airybiprime(0) == root(3, 6) / gamma(Rational(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) == (root(3, 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))) + root(3, 6) * hyper(
(), (Rational(1, 3), ), z**3 / 9) / gamma(Rational(1, 3)))
assert isinstance(airybiprime(z).rewrite(besselj), airybiprime)
assert (airybiprime(t).rewrite(besselj) == -sqrt(3) * t *
(besselj(-Rational(2, 3), 2 * (-t)**Rational(3, 2) / 3) +
besselj(Rational(2, 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 airybiprime(p).rewrite(besselj) == airybiprime(p)
assert expand_func(airybiprime(
2 *
cbrt(3 * z**5))) == (sqrt(3) * (z**Rational(5, 3) / cbrt(z**5) - 1) *
airyaiprime(2 * cbrt(3) * z**Rational(5, 3)) / 2 +
(z**Rational(5, 3) / cbrt(z**5) + 1) *
airybiprime(2 * cbrt(3) * z**Rational(5, 3)) / 2)
assert expand_func(airybiprime(x * y)) == airybiprime(x * y)
assert expand_func(airybiprime(log(x))) == airybiprime(log(x))
assert expand_func(airybiprime(2 * root(3 * z**5, 5))) == airybiprime(
2 * root(3 * z**5, 5))
assert airybiprime(-2).evalf(50) == Float(
'0.27879516692116952268509756941098324140300059345163131', dps=50)
def test_airyaiprime():
z = Symbol('z', extended_real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airyaiprime(z), airyaiprime)
assert airyaiprime(0) == -3**Rational(2, 3) / (3 * gamma(Rational(1, 3)))
assert airyaiprime(oo) == 0
assert diff(airyaiprime(z), z) == z * airyai(z)
assert series(airyaiprime(z), z, 0,
3) == (-3**Rational(2, 3) / (3 * gamma(Rational(1, 3))) +
cbrt(3) * z**2 / (6 * gamma(Rational(2, 3))) +
O(z**3))
assert airyaiprime(z).rewrite(hyper) == (
cbrt(3) * z**2 * hyper((), (Rational(5, 3), ), z**3 / 9) /
(6 * gamma(Rational(2, 3))) - 3**Rational(2, 3) * hyper(
(), (Rational(1, 3), ), z**3 / 9) / (3 * gamma(Rational(1, 3))))
assert isinstance(airyaiprime(z).rewrite(besselj), airyaiprime)
assert (airyaiprime(t).rewrite(besselj) == t *
(besselj(-Rational(2, 3), 2 * (-t)**Rational(3, 2) / 3) -
besselj(Rational(2, 3), 2 * (-t)**Rational(3, 2) / 3)) / 3)
assert airyaiprime(z).rewrite(besseli) == (
z**2 * besseli(Rational(2, 3), 2 * z**Rational(3, 2) / 3) /
(3 * (z**Rational(3, 2))**Rational(2, 3)) -
(z**Rational(3, 2))**Rational(2, 3) *
besseli(-Rational(1, 3), 2 * z**Rational(3, 2) / 3) / 3)
assert airyaiprime(p).rewrite(besseli) == (
p * (-besseli(-Rational(2, 3), 2 * p**Rational(3, 2) / 3) +
besseli(Rational(2, 3), 2 * p**Rational(3, 2) / 3)) / 3)
assert airyaiprime(p).rewrite(besselj) == airyaiprime(p)
assert expand_func(airyaiprime(
2 *
cbrt(3 * z**5))) == (sqrt(3) * (z**Rational(5, 3) / cbrt(z**5) - 1) *
airybiprime(2 * cbrt(3) * z**Rational(5, 3)) / 6 +
(z**Rational(5, 3) / cbrt(z**5) + 1) *
airyaiprime(2 * cbrt(3) * z**Rational(5, 3)) / 2)
assert expand_func(airyaiprime(x * y)) == airyaiprime(x * y)
assert expand_func(airyaiprime(log(x))) == airyaiprime(log(x))
assert expand_func(airyaiprime(2 * root(3 * z**5, 5))) == airyaiprime(
2 * root(3 * z**5, 5))
assert airyaiprime(-2).evalf(50) == Float(
'0.61825902074169104140626429133247528291577794512414753', dps=50)
def test_bessel():
from diofant 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 + Rational(1, 2))),
(x, 1, oo), meijerg=True, conds='none')
* 2/((z/2)**y*sqrt(pi)*gamma(Rational(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_meijerg_eval():
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).evalf(subs={x: x_, k: k_}, strict=False)) < 1e-10
assert abs((expr1 - expr2).evalf(subs={x: x_, k: -k_}, strict=False)) < 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, Rational(1, 3), 0.25, 0.75, Rational(2, 3), 1.0, 1.5]:
assert abs((expr1 - expr2).evalf(
subs={x: x_, k: k_ + eps, l: k_ - eps})) < 1e-10
assert abs((expr1 - expr2).evalf(
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)).evalf(chop=True) == 0
def test_meijerg_eval():
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).evalf(subs={x: x_, k: k_}, strict=False)) < 1e-10
assert abs((expr1 - expr2).evalf(subs={x: x_, k: -k_}, strict=False)) < 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, Rational(1, 3), 0.25, 0.75, Rational(2, 3), 1.0, 1.5]:
assert abs((expr1 - expr2).evalf(
subs={x: x_, k: k_ + eps, l: k_ - eps})) < 1e-10
assert abs((expr1 - expr2).evalf(
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)).evalf(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():
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 + Rational(1, 2))),
(x, 1, oo), meijerg=True, conds='none')
* 2/((z/2)**y*sqrt(pi)*gamma(Rational(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_airyai():
z = Symbol('z', extended_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**Integer(3) / 9) / (3 * gamma(Rational(1, 3))) +
3**Rational(1, 3) * hyper(
(), (Rational(2, 3), ),
z**Integer(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_airybi():
z = Symbol('z', extended_real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airybi(z), airybi)
assert airybi(0) == 3**Rational(5, 6)/(3*gamma(Rational(2, 3)))
assert airybi(oo) == oo
assert airybi(-oo) == 0
assert diff(airybi(z), z) == airybiprime(z)
assert series(airybi(z), z, 0, 3) == (
cbrt(3)*gamma(Rational(1, 3))/(2*pi) + 3**Rational(2, 3)*z*gamma(Rational(2, 3))/(2*pi) + O(z**3))
l = Limit(airybi(I/x)/(exp(Rational(2, 3)*(I/x)**Rational(3, 2))*sqrt(pi*sqrt(I/x))), x, 0)
assert l.doit() == l
assert airybi(z).rewrite(hyper) == (
root(3, 6)*z*hyper((), (Rational(4, 3),), z**3/9)/gamma(Rational(1, 3)) +
3**Rational(5, 6)*hyper((), (Rational(2, 3),), z**3/9)/(3*gamma(Rational(2, 3))))
assert isinstance(airybi(z).rewrite(besselj), airybi)
assert (airybi(t).rewrite(besselj) ==
sqrt(3)*sqrt(-t)*(besselj(-1/3, 2*(-t)**Rational(3, 2)/3) -
besselj(Rational(1, 3),
2*(-t)**Rational(3, 2)/3))/3)
assert airybi(z).rewrite(besseli) == (
sqrt(3)*(z*besseli(Rational(1, 3), 2*z**Rational(3, 2)/3)/cbrt(z**Rational(3, 2)) +
cbrt(z**Rational(3, 2))*besseli(-Rational(1, 3), 2*z**Rational(3, 2)/3))/3)
assert airybi(p).rewrite(besseli) == (
sqrt(3)*sqrt(p)*(besseli(-Rational(1, 3), 2*p**Rational(3, 2)/3) +
besseli(Rational(1, 3), 2*p**Rational(3, 2)/3))/3)
assert airybi(p).rewrite(besselj) == airybi(p)
assert expand_func(airybi(2*cbrt(3*z**5))) == (
sqrt(3)*(1 - cbrt(z**5)/z**Rational(5, 3))*airyai(2*cbrt(3)*z**Rational(5, 3))/2 +
(1 + cbrt(z**5)/z**Rational(5, 3))*airybi(2*cbrt(3)*z**Rational(5, 3))/2)
assert expand_func(airybi(x*y)) == airybi(x*y)
assert expand_func(airybi(log(x))) == airybi(log(x))
assert expand_func(airybi(2*root(3*z**5, 5))) == airybi(2*root(3*z**5, 5))
assert airybi(x).taylor_term(-1, x) == 0
def test_bessel_eval():
n, m, k = Symbol('n', integer=True), Symbol('m'), Symbol('k',
integer=True,
zero=False)
for f in [besselj, besseli]:
assert f(0, 0) == 1
assert f(2.1, 0) == 0
assert f(-3, 0) == 0
assert f(-10.2, 0) == zoo
assert f(1 + 3 * I, 0) == 0
assert f(-3 + I, 0) == zoo
assert f(-2 * I, 0) == nan
assert f(n, 0) not in (0, 1)
assert f(m, 0) not in (0, 1)
assert f(k, 0) == 0
assert bessely(0, 0) == -oo
assert besselk(0, 0) == +oo
for f in [bessely, besselk]:
assert f(1 + I, 0) == zoo
assert f(I, 0) == nan
for x in (oo, -oo, I * oo, -I * oo):
assert besselk(m, x) == 0
for f in [besselj, bessely]:
assert f(m, +oo) == 0
assert f(m, -oo) == 0
for f in [besseli, besselk]:
assert f(m, +I * oo) == 0
assert f(m, -I * oo) == 0
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_bessel_eval():
from diofant 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_rewrite():
assert besselj(
n, z).rewrite(jn) == sqrt(2 * z / pi) * jn(n - Rational(1, 2), z)
assert bessely(
n, z).rewrite(yn) == sqrt(2 * z / pi) * yn(n - Rational(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)
assert besselj(2, z).rewrite(bessely) == besselj(2, z)
assert bessely(2, z).rewrite(besselj) == bessely(2, z)
assert bessely(2, z).rewrite(besseli) == bessely(2, z)
assert besselk(2, z).rewrite(besseli) == besselk(2, z)
assert besselk(2, z).rewrite(besselj) == besselk(2, z)
assert besselk(2, z).rewrite(bessely) == besselk(2, 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)
def test_rewrite():
assert besselj(n, z).rewrite(jn) == sqrt(2*z/pi)*jn(n - Rational(1, 2), z)
assert bessely(n, z).rewrite(yn) == sqrt(2*z/pi)*yn(n - Rational(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)
assert besselj(2, z).rewrite(bessely) == besselj(2, z)
assert bessely(2, z).rewrite(besselj) == bessely(2, z)
assert bessely(2, z).rewrite(besseli) == bessely(2, z)
assert besselk(2, z).rewrite(besseli) == besselk(2, z)
assert besselk(2, z).rewrite(besselj) == besselk(2, z)
assert besselk(2, z).rewrite(bessely) == besselk(2, 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)
def test_airybiprime():
z = Symbol('z', extended_real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airybiprime(z), airybiprime)
assert airybiprime(0) == root(3, 6)/gamma(Rational(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) == (
root(3, 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))) +
root(3, 6)*hyper((), (Rational(1, 3),), z**3/9)/gamma(Rational(1, 3)))
assert isinstance(airybiprime(z).rewrite(besselj), airybiprime)
assert (airybiprime(t).rewrite(besselj) ==
-sqrt(3)*t*(besselj(-Rational(2, 3), 2*(-t)**Rational(3, 2)/3) +
besselj(Rational(2, 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 airybiprime(p).rewrite(besselj) == airybiprime(p)
assert expand_func(airybiprime(2*cbrt(3*z**5))) == (
sqrt(3)*(z**Rational(5, 3)/cbrt(z**5) - 1)*airyaiprime(2*cbrt(3)*z**Rational(5, 3))/2 +
(z**Rational(5, 3)/cbrt(z**5) + 1)*airybiprime(2*cbrt(3)*z**Rational(5, 3))/2)
assert expand_func(airybiprime(x*y)) == airybiprime(x*y)
assert expand_func(airybiprime(log(x))) == airybiprime(log(x))
assert expand_func(airybiprime(2*root(3*z**5, 5))) == airybiprime(2*root(3*z**5, 5))
assert airybiprime(-2).evalf(50) == Float('0.27879516692116952268509756941098324140300059345163131', dps=50)
def test_airyaiprime():
z = Symbol('z', extended_real=False)
t = Symbol('t', negative=True)
p = Symbol('p', positive=True)
assert isinstance(airyaiprime(z), airyaiprime)
assert airyaiprime(0) == -3**Rational(2, 3)/(3*gamma(Rational(1, 3)))
assert airyaiprime(oo) == 0
assert diff(airyaiprime(z), z) == z*airyai(z)
assert series(airyaiprime(z), z, 0, 3) == (
-3**Rational(2, 3)/(3*gamma(Rational(1, 3))) + cbrt(3)*z**2/(6*gamma(Rational(2, 3))) + O(z**3))
assert airyaiprime(z).rewrite(hyper) == (
cbrt(3)*z**2*hyper((), (Rational(5, 3),), z**3/9)/(6*gamma(Rational(2, 3))) -
3**Rational(2, 3)*hyper((), (Rational(1, 3),), z**3/9)/(3*gamma(Rational(1, 3))))
assert isinstance(airyaiprime(z).rewrite(besselj), airyaiprime)
assert (airyaiprime(t).rewrite(besselj) ==
t*(besselj(-Rational(2, 3), 2*(-t)**Rational(3, 2)/3) -
besselj(Rational(2, 3), 2*(-t)**Rational(3, 2)/3))/3)
assert airyaiprime(z).rewrite(besseli) == (
z**2*besseli(Rational(2, 3), 2*z**Rational(3, 2)/3)/(3*(z**Rational(3, 2))**Rational(2, 3)) -
(z**Rational(3, 2))**Rational(2, 3)*besseli(-Rational(1, 3), 2*z**Rational(3, 2)/3)/3)
assert airyaiprime(p).rewrite(besseli) == (
p*(-besseli(-Rational(2, 3), 2*p**Rational(3, 2)/3) + besseli(Rational(2, 3), 2*p**Rational(3, 2)/3))/3)
assert airyaiprime(p).rewrite(besselj) == airyaiprime(p)
assert expand_func(airyaiprime(2*cbrt(3*z**5))) == (
sqrt(3)*(z**Rational(5, 3)/cbrt(z**5) - 1)*airybiprime(2*cbrt(3)*z**Rational(5, 3))/6 +
(z**Rational(5, 3)/cbrt(z**5) + 1)*airyaiprime(2*cbrt(3)*z**Rational(5, 3))/2)
assert expand_func(airyaiprime(x*y)) == airyaiprime(x*y)
assert expand_func(airyaiprime(log(x))) == airyaiprime(log(x))
assert expand_func(airyaiprime(2*root(3*z**5, 5))) == airyaiprime(2*root(3*z**5, 5))
assert airyaiprime(-2).evalf(50) == Float('0.61825902074169104140626429133247528291577794512414753', dps=50)
def test_bessel_eval():
n, m, k = Symbol('n', integer=True), Symbol('m'), Symbol('k', integer=True, zero=False)
for f in [besselj, besseli]:
assert f(0, 0) == 1
assert f(2.1, 0) == 0
assert f(-3, 0) == 0
assert f(-10.2, 0) == zoo
assert f(1 + 3*I, 0) == 0
assert f(-3 + I, 0) == zoo
assert f(-2*I, 0) == nan
assert f(n, 0) not in (0, 1)
assert f(m, 0) not in (0, 1)
assert f(k, 0) == 0
assert bessely(0, 0) == -oo
assert besselk(0, 0) == +oo
for f in [bessely, besselk]:
assert f(1 + I, 0) == zoo
assert f(I, 0) == nan
for f in [besselj, bessely]:
assert f(m, +oo) == 0
assert f(m, -oo) == 0
for f in [besseli, besselk]:
assert f(m, +I*oo) == 0
assert f(m, -I*oo) == 0
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+Rational(-1, 2)], [2*a]
assert hyperexpand(hyper([1, 2], [3], z)) == -2/z - 2*log(-z + 1)/z**2
assert hyperexpand(hyper([Rational(1, 2), 2], [Rational(3, 2)], z)) == \
-1/(2*z - 2) + atanh(sqrt(z))/sqrt(z)/2
assert hyperexpand(hyper([Rational(1, 2), Rational(1, 2)], [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], [Rational(1, 2), 3], z)) == \
sqrt(z)*(6*z/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 + Rational(1, 2), 1, 1], [2, 2], z)) == \
-4*log(sqrt(-z + 1)/2 + Rational(1, 2))/z
# TODO hyperexpand(hyper([a], [2*a + 1], z))
# TODO [Rational(1, 2), a], [Rational(3, 2), a+1]
assert hyperexpand(hyper([2], [b, 1], z)) == \
z**(-b/2 + Rational(1, 2))*besseli(b - 1, 2*sqrt(z))*gamma(b) \
+ z**(-b/2 + 1)*besseli(b, 2*sqrt(z))*gamma(b)
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], [Rational(3, 2)], z)) == \
-1/(2*z - 2) + atanh(sqrt(z))/sqrt(z)/2
assert hyperexpand(hyper([Rational(1, 2), Rational(1, 2)], [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([-S.Half - 1, 1, 2], [S.Half, 3], z)) == \
sqrt(z)*(6*z/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 + Rational(1, 2))/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 + Rational(1, 2))*besseli(b - 1, 2*sqrt(z))*gamma(b) \
+ z**(-b/2 + 1)*besseli(b, 2*sqrt(z))*gamma(b)
def test_inverse_laplace_transform():
from diofant 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_inverse_laplace_transform():
ILT = inverse_laplace_transform
a, b, c, = symbols('a b c', positive=True, finite=True)
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():
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)*root(x, 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
def test_mellin_transform_bessel():
from diofant import Max
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, Rational(3, 4)), True)
assert MT(sin(sqrt(x))*besselj(a, sqrt(x)), x, s) == \
(2**a*gamma(-2*s + Rational(1, 2))*gamma(a/2 + s + Rational(1, 2))/(
gamma(-a/2 - s + 1)*gamma(a - 2*s + 1)), (
-re(a)/2 - Rational(1, 2), Rational(1, 4)), True)
assert MT(cos(sqrt(x))*besselj(a, sqrt(x)), x, s) == \
(2**a*gamma(a/2 + s)*gamma(-2*s + Rational(1, 2))/(
gamma(-a/2 - s + Rational(1, 2))*gamma(a - 2*s + 1)), (
-re(a)/2, Rational(1, 4)), True)
assert MT(besselj(a, sqrt(x))**2, x, s) == \
(gamma(a + s)*gamma(Rational(1, 2) - s)
/ (sqrt(pi)*gamma(1 - s)*gamma(1 + a - s)),
(-re(a), Rational(1, 2)), True)
assert MT(besselj(a, sqrt(x))*besselj(-a, sqrt(x)), x, s) == \
(gamma(s)*gamma(Rational(1, 2) - s)
/ (sqrt(pi)*gamma(1 - a - s)*gamma(1 + a - s)),
(0, Rational(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 - Rational(1, 2))
/ (sqrt(pi)*gamma(Rational(3, 2) - s)*gamma(a - s + Rational(1, 2))),
(Rational(1, 2) - re(a), Rational(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, Rational(1, 2)), True)
assert MT(besselj(a, sqrt(x))**2 + besselj(-a, sqrt(x))**2, x, s)[1:] == \
((Max(re(a), -re(a)), Rational(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), Rational(3, 4)), True)
assert MT(sin(sqrt(x))*bessely(a, sqrt(x)), x, s) == \
(-4**s*sin(pi*(a/2 - s))*gamma(Rational(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), Rational(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(Rational(1, 2) - 2*s)
/ (sqrt(pi)*gamma(Rational(1, 2) - s - a/2)*gamma(Rational(1, 2) - s + a/2)),
(Max(-re(a)/2, re(a)/2), Rational(1, 4)), True)
assert MT(besselj(a, sqrt(x))*bessely(a, sqrt(x)), x, s) == \
(-cos(pi*s)*gamma(s)*gamma(a + s)*gamma(Rational(1, 2) - s)
/ (pi**Rational(3, 2)*gamma(1 + a - s)),
(Max(-re(a), 0), Rational(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), Rational(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)), Rational(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 + Rational(1, 2))/(2*sqrt(pi)*gamma(a - s + 1)),
(Max(-re(a), 0), Rational(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), Rational(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**Rational(3, 2) * cos(
pi * s) * gamma(-s + Rational(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
mu1, mu2 = symbols('mu1 mu2', real=True, nonzero=True)
sigma1, sigma2 = symbols('sigma1 sigma2',
real=True,
nonzero=True,
positive=True)
rate = Symbol('lambda', real=True, positive=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, real=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)) == \
Piecewise((gamma(a + b)*gamma(a + y)/(gamma(a)*gamma(a + b + y)),
-a - re(y) + 1 < 1),
(Integral(x**(a + y - 1)*(-x + 1)**(b - 1)*gamma(a + b)/(gamma(a)*gamma(b)),
(x, 0, 1)), True))
# 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, real=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**(-Rational(3, 2)) * exp(
-lamda * (x - mu)**2 / x / 2 / mu**2)
def mysimp(expr):
return 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)**Rational(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, real=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
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', extended_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 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_expand():
assert expand_func(besselj(Rational(1, 2), z).rewrite(jn)) == \
sqrt(2)*sin(z)/(sqrt(pi)*sqrt(z))
assert expand_func(bessely(Rational(1, 2), z).rewrite(yn)) == \
-sqrt(2)*cos(z)/(sqrt(pi)*sqrt(z))
assert expand_func(besselj(I, z)) == besselj(I, z)
# Test simplify helper
assert simplify(besselj(Rational(1, 2), z)) == sqrt(2)*sin(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(Rational(1, 2), z)) == sqrt(2)*sin(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besselj(Rational(-1, 2), z)) == sqrt(2)*cos(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besselj(Rational(5, 2), z)) == \
-sqrt(2)*(z**2*sin(z) + 3*z*cos(z) - 3*sin(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(besselj(-Rational(5, 2), z)) == \
-sqrt(2)*(z**2*cos(z) - 3*z*sin(z) - 3*cos(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(bessely(Rational(1, 2), z)) == \
-(sqrt(2)*cos(z))/(sqrt(pi)*sqrt(z))
assert besselsimp(bessely(Rational(-1, 2), z)) == sqrt(2)*sin(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(bessely(Rational(5, 2), z)) == \
sqrt(2)*(z**2*cos(z) - 3*z*sin(z) - 3*cos(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(bessely(Rational(-5, 2), z)) == \
-sqrt(2)*(z**2*sin(z) + 3*z*cos(z) - 3*sin(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(besseli(Rational(1, 2), z)) == sqrt(2)*sinh(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besseli(Rational(-1, 2), z)) == \
sqrt(2)*cosh(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besseli(Rational(5, 2), z)) == \
sqrt(2)*(z**2*sinh(z) - 3*z*cosh(z) + 3*sinh(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(besseli(Rational(-5, 2), z)) == \
sqrt(2)*(z**2*cosh(z) - 3*z*sinh(z) + 3*cosh(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(besselk(Rational(1, 2), z)) == \
besselsimp(besselk(Rational(-1, 2), z)) == sqrt(pi)*exp(-z)/(sqrt(2)*sqrt(z))
assert besselsimp(besselk(Rational(5, 2), z)) == \
besselsimp(besselk(Rational(-5, 2), z)) == \
sqrt(2)*sqrt(pi)*(z**2 + 3*z + 3)*exp(-z)/(2*z**Rational(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 = Rational(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 + Rational(1, 2), z).rewrite(jn)) == \
(sqrt(2)*sqrt(z)*exp(-I*pi*(n + Rational(1, 2))/2) *
exp_polar(I*pi/4)*jn(n, z*exp_polar(I*pi/2))/sqrt(pi))
assert expand_func(besselj(n + Rational(1, 2), z).rewrite(jn)) == \
sqrt(2)*sqrt(z)*jn(n, z)/sqrt(pi)
r = Symbol('r', extended_real=True)
p = Symbol('p', positive=True)
i = Symbol('i', integer=True)
for besselx in [besselj, bessely, besseli, besselk]:
assert besselx(i, p).is_extended_real
assert besselx(i, x).is_extended_real is None
assert besselx(x, z).is_extended_real is None
for besselx in [besselj, besseli]:
assert besselx(i, r).is_extended_real
for besselx in [bessely, besselk]:
assert besselx(i, r).is_extended_real is None
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():
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, Rational(3, 4)), True)
assert MT(sin(sqrt(x))*besselj(a, sqrt(x)), x, s) == \
(2**a*gamma(-2*s + Rational(1, 2))*gamma(a/2 + s + Rational(1, 2))/(
gamma(-a/2 - s + 1)*gamma(a - 2*s + 1)), (
-re(a)/2 - Rational(1, 2), Rational(1, 4)), True)
assert MT(cos(sqrt(x))*besselj(a, sqrt(x)), x, s) == \
(2**a*gamma(a/2 + s)*gamma(-2*s + Rational(1, 2))/(
gamma(-a/2 - s + Rational(1, 2))*gamma(a - 2*s + 1)), (
-re(a)/2, Rational(1, 4)), True)
assert MT(besselj(a, sqrt(x))**2, x, s) == \
(gamma(a + s)*gamma(Rational(1, 2) - s)
/ (sqrt(pi)*gamma(1 - s)*gamma(1 + a - s)),
(-re(a), Rational(1, 2)), True)
assert MT(besselj(a, sqrt(x))*besselj(-a, sqrt(x)), x, s) == \
(gamma(s)*gamma(Rational(1, 2) - s)
/ (sqrt(pi)*gamma(1 - a - s)*gamma(1 + a - s)),
(0, Rational(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 - Rational(1, 2))
/ (sqrt(pi)*gamma(Rational(3, 2) - s)*gamma(a - s + Rational(1, 2))),
(Rational(1, 2) - re(a), Rational(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, Rational(1, 2)), True)
assert MT(besselj(a, sqrt(x))**2 + besselj(-a, sqrt(x))**2, x, s)[1:] == \
((Max(re(a), -re(a)), Rational(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), Rational(3, 4)), True)
assert MT(sin(sqrt(x))*bessely(a, sqrt(x)), x, s) == \
(-4**s*sin(pi*(a/2 - s))*gamma(Rational(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), Rational(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(Rational(1, 2) - 2*s)
/ (sqrt(pi)*gamma(Rational(1, 2) - s - a/2)*gamma(Rational(1, 2) - s + a/2)),
(Max(-re(a)/2, re(a)/2), Rational(1, 4)), True)
assert MT(besselj(a, sqrt(x))*bessely(a, sqrt(x)), x, s) == \
(-cos(pi*s)*gamma(s)*gamma(a + s)*gamma(Rational(1, 2) - s)
/ (pi**Rational(3, 2)*gamma(1 + a - s)),
(Max(-re(a), 0), Rational(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), Rational(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)), Rational(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 + Rational(1, 2))/(2*sqrt(pi)*gamma(a - s + 1)),
(Max(-re(a), 0), Rational(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), Rational(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**Rational(3, 2)*cos(pi*s)*gamma(-s + Rational(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_expand():
assert expand_func(besselj(Rational(1, 2), z).rewrite(jn)) == \
sqrt(2)*sin(z)/(sqrt(pi)*sqrt(z))
assert expand_func(bessely(Rational(1, 2), z).rewrite(yn)) == \
-sqrt(2)*cos(z)/(sqrt(pi)*sqrt(z))
assert expand_func(besselj(I, z)) == besselj(I, z)
# Test simplify helper
assert simplify(besselj(Rational(1, 2),
z)) == sqrt(2) * sin(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(Rational(1, 2),
z)) == sqrt(2) * sin(z) / (sqrt(pi) * sqrt(z))
assert besselsimp(besselj(Rational(-1, 2),
z)) == sqrt(2) * cos(z) / (sqrt(pi) * sqrt(z))
assert besselsimp(besselj(Rational(5, 2), z)) == \
-sqrt(2)*(z**2*sin(z) + 3*z*cos(z) - 3*sin(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(besselj(-Rational(5, 2), z)) == \
-sqrt(2)*(z**2*cos(z) - 3*z*sin(z) - 3*cos(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(bessely(Rational(1, 2), z)) == \
-(sqrt(2)*cos(z))/(sqrt(pi)*sqrt(z))
assert besselsimp(bessely(Rational(-1, 2),
z)) == sqrt(2) * sin(z) / (sqrt(pi) * sqrt(z))
assert besselsimp(bessely(Rational(5, 2), z)) == \
sqrt(2)*(z**2*cos(z) - 3*z*sin(z) - 3*cos(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(bessely(Rational(-5, 2), z)) == \
-sqrt(2)*(z**2*sin(z) + 3*z*cos(z) - 3*sin(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(besseli(Rational(1, 2),
z)) == sqrt(2) * sinh(z) / (sqrt(pi) * sqrt(z))
assert besselsimp(besseli(Rational(-1, 2), z)) == \
sqrt(2)*cosh(z)/(sqrt(pi)*sqrt(z))
assert besselsimp(besseli(Rational(5, 2), z)) == \
sqrt(2)*(z**2*sinh(z) - 3*z*cosh(z) + 3*sinh(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(besseli(Rational(-5, 2), z)) == \
sqrt(2)*(z**2*cosh(z) - 3*z*sinh(z) + 3*cosh(z))/(sqrt(pi)*z**Rational(5, 2))
assert besselsimp(besselk(Rational(1, 2), z)) == \
besselsimp(besselk(Rational(-1, 2), z)) == sqrt(pi)*exp(-z)/(sqrt(2)*sqrt(z))
assert besselsimp(besselk(Rational(5, 2), z)) == \
besselsimp(besselk(Rational(-5, 2), z)) == \
sqrt(2)*sqrt(pi)*(z**2 + 3*z + 3)*exp(-z)/(2*z**Rational(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 = Rational(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 + Rational(1, 2), z).rewrite(jn)) == \
(sqrt(2)*sqrt(z)*exp(-I*pi*(n + Rational(1, 2))/2) *
exp_polar(I*pi/4)*jn(n, z*exp_polar(I*pi/2))/sqrt(pi))
assert expand_func(besselj(n + Rational(1, 2), z).rewrite(jn)) == \
sqrt(2)*sqrt(z)*jn(n, z)/sqrt(pi)
r = Symbol('r', extended_real=True)
p = Symbol('p', positive=True)
i = Symbol('i', integer=True)
for besselx in [besselj, bessely, besseli, besselk]:
assert besselx(i, p).is_extended_real
assert besselx(i, x).is_extended_real is None
assert besselx(x, z).is_extended_real is None
for besselx in [besselj, besseli]:
assert besselx(i, r).is_extended_real
for besselx in [bessely, besselk]:
assert besselx(i, r).is_extended_real is None
def test_probability():
# various integrals from probability theory
mu1, mu2 = symbols('mu1 mu2', real=True, nonzero=True)
sigma1, sigma2 = symbols('sigma1 sigma2', real=True,
nonzero=True, positive=True)
rate = Symbol('lambda', real=True, positive=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**(-Rational(3, 2))*exp(-lamda*(x - mu)**2/x/2/mu**2)
def mysimp(expr):
return 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)**Rational(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
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', extended_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 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))
