gamma_functions.py 文件源码

def upper_incomplete_gamma(a,x,d=0,iterations=100):
    if d == iterations:
        if ((d % 2) == 1):
            return 1.0 # end iterations
        else:
            m = d/2
            return x + (m-a)
    if d == 0:
        result = ((x**a) * (e**(-x)))/upper_incomplete_gamma(a,x,d=d+1)
        return result
    elif ((d % 2) == 1):
        m = 1.0+((d-1.0)/2.0)
        return x+ ((m-a)/(upper_incomplete_gamma(a,x,d=d+1)))
    else:
        m = d/2
        return 1+(m/(upper_incomplete_gamma(a,x,d=d+1)))

# 6.5.31 Handbook of Mathematical Functions, page 263
#    Recursive implementation