# HG changeset patch
# User Jeff Hammel <k0scist@gmail.com>
# Date 1504481923 25200
# Node ID bf8bd42f8cd7661c7cc0460de91255f78376597f
# Parent  b95fe82ac9ce94030904ab4fadb170fda1dae9f2
[sigmoid] use numpy + add docstring

diff -r b95fe82ac9ce -r bf8bd42f8cd7 tvii/sigmoid.py
--- a/tvii/sigmoid.py	Sun Sep 03 13:17:33 2017 -0700
+++ b/tvii/sigmoid.py	Sun Sep 03 16:38:43 2017 -0700
@@ -2,7 +2,9 @@
 sigmoid function: 1/(1 + e^-z)
 """
 
-import math
+import numpy as np
+
 
 def sigmoid(z):
-    return 1./(1. + math.exp(-z))
+    """https://en.wikipedia.org/wiki/Sigmoid_function"""
+    return 1./(1. + np.exp(-z))