gamma_functions.py 文件源码

def lower_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)))/lower_incomplete_gamma(a,x,d=d+1)
        return result
    elif ((d % 2) == 1):
        m = d - 1
        n = (d-1.0)/2.0
        return a + m - (((a+n)*x)/lower_incomplete_gamma(a,x,d=d+1))
    else:
        m = d-1
        n = d/2.0
        return a+m+((n*x)/(lower_incomplete_gamma(a,x,d=d+1)))