__init__.py 文件源码

def inv_psi(y, tol=1e-10, n_iter=100, psi=psi):
    """
    Inverse digamma function
    """
    from numpy import exp
    from scipy.special import digamma
    ## initial value

    if y < -5 / 3. - EULER_MASCHERONI:
        x = -1 / (EULER_MASCHERONI + y)
    else:
        x = 0.5 + exp(y)

    ## Newton root finding

    for dummy in range(n_iter):

        z = digamma(x) - y

        if abs(z) < tol:
            break

        x -= z / d_approx_psi(x)

    return x