transfer.py 文件源码

def logistic(x, prime=0):
    if prime == 0:
        ##v = np.empty_like(x)
        ##mask = x < 0.0

        ##zl = np.exp(x[mask])
        ##zl = 1.0 / (1.0 + zl)
        ##v[mask] = zl

        ##zh = np.exp(-x[~mask])
        ##zh = zh / (1.0 + zh)
        ##v[~mask] = zh

        v = sps.expit(x)

        return v

    elif prime == 1:
        return logistic(x) * (1.0 - logistic(x))

    else:
        raise NotImplementedError('%d order derivative not implemented.' % int(prime))