def test_gegenbauer_poly(): raises(ValueError, lambda: gegenbauer_poly(-1, a, x)) assert gegenbauer_poly(1, a, x, polys=True) == Poly(2*a*x, x, domain='ZZ(a)') assert gegenbauer_poly(0, a, x) == 1 assert gegenbauer_poly(1, a, x) == 2*a*x assert gegenbauer_poly(2, a, x) == -a + x**2*(2*a**2 + 2*a) assert gegenbauer_poly(3, a, x) == x**3*(4*a**3/3 + 4*a**2 + 8*a/3) + x*(-2*a**2 - 2*a) assert gegenbauer_poly(1, S.Half).dummy_eq(x) assert gegenbauer_poly(1, a, polys=True) == Poly(2*a*x, x, domain='ZZ(a)')
def test_gegenbauer_poly(): raises(ValueError, lambda: gegenbauer_poly(-1, a, x)) assert gegenbauer_poly( 1, a, x, polys=True) == Poly(2*a*x, x, domain='ZZ(a)') assert gegenbauer_poly(0, a, x) == 1 assert gegenbauer_poly(1, a, x) == 2*a*x assert gegenbauer_poly(2, a, x) == -a + x**2*(2*a**2 + 2*a) assert gegenbauer_poly( 3, a, x) == x**3*(4*a**3/3 + 4*a**2 + 8*a/3) + x*(-2*a**2 - 2*a) assert gegenbauer_poly(1, S.Half).dummy_eq(x) assert gegenbauer_poly(1, a, polys=True) == Poly(2*a*x, x, domain='ZZ(a)')
def eval(cls, n, a, x): # For negative n the polynomials vanish # See http://functions.wolfram.com/Polynomials/GegenbauerC3/03/01/03/0012/ if n.is_negative: return S.Zero # Some special values for fixed a if a == S.Half: return legendre(n, x) elif a == S.One: return chebyshevu(n, x) elif a == S.NegativeOne: return S.Zero if not n.is_Number: # Handle this before the general sign extraction rule if x == S.NegativeOne: if (re(a) > S.Half) == True: return S.ComplexInfinity else: return ( cos(S.Pi * (a + n)) * sec(S.Pi * a) * gamma(2 * a + n) / (gamma(2 * a) * gamma(n + 1)) ) # Symbolic result C^a_n(x) # C^a_n(-x) ---> (-1)**n * C^a_n(x) if x.could_extract_minus_sign(): return S.NegativeOne ** n * gegenbauer(n, a, -x) # We can evaluate for some special values of x if x.is_zero: return ( 2 ** n * sqrt(S.Pi) * gamma(a + S.Half * n) / (gamma((1 - n) / 2) * gamma(n + 1) * gamma(a)) ) if x == S.One: return gamma(2 * a + n) / (gamma(2 * a) * gamma(n + 1)) elif x is S.Infinity: if n.is_positive: return RisingFactorial(a, n) * S.Infinity else: # n is a given fixed integer, evaluate into polynomial return gegenbauer_poly(n, a, x)
def eval(cls, n, a, x): # For negative n the polynomials vanish # See http://functions.wolfram.com/Polynomials/GegenbauerC3/03/01/03/0012/ if n.is_negative: return S.Zero # Some special values for fixed a if a == S.Half: return legendre(n, x) elif a == S.One: return chebyshevu(n, x) elif a == S.NegativeOne: return S.Zero if not n.is_Number: # Handle this before the general sign extraction rule if x == S.NegativeOne: if (C.re(a) > S.Half) == True: return S.ComplexInfinity else: # No sec function available yet # return (C.cos(S.Pi*(a+n)) * C.sec(S.Pi*a) * C.gamma(2*a+n) / # (C.gamma(2*a) * C.gamma(n+1))) return None # Symbolic result C^a_n(x) # C^a_n(-x) ---> (-1)**n * C^a_n(x) if x.could_extract_minus_sign(): return S.NegativeOne ** n * gegenbauer(n, a, -x) # We can evaluate for some special values of x if x == S.Zero: return ( 2 ** n * sqrt(S.Pi) * C.gamma(a + S.Half * n) / (C.gamma((1 - n) / 2) * C.gamma(n + 1) * C.gamma(a)) ) if x == S.One: return C.gamma(2 * a + n) / (C.gamma(2 * a) * C.gamma(n + 1)) elif x == S.Infinity: if n.is_positive: return C.RisingFactorial(a, n) * S.Infinity else: # n is a given fixed integer, evaluate into polynomial return gegenbauer_poly(n, a, x)