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_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_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_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_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_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, 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)