view tvii/sigmoid.py @ 52:0b3daccfc36c

[documentation] link to lore python lib
author Jeff Hammel <k0scist@gmail.com>
date Sat, 23 Sep 2017 11:18:15 -0700
parents 38aa9098bf2d
children
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"""
sigmoid function: 1/(1 + e^-z)
"""

import numpy as np
from .iterable import isiterable

def sigmoid(z):
    """https://en.wikipedia.org/wiki/Sigmoid_function"""
    if not isinstance(z, np.ndarray) and isiterable(z):
        z = np.array(z)
    return 1./(1. + np.exp(-z))


def sigmoidprime(z):
    """"derivative of sigmoid"""
    return sigmoid(z)*(1-sigmoid(z))