diff --git a/lib/nn.js b/lib/nn.js
index 0cb4527..4e61c92 100644
--- a/lib/nn.js
+++ b/lib/nn.js
@@ -17,6 +17,11 @@ let tanh = new ActivationFunction(
   y => 1 - (y * y)
 );
 
+let tanh = new ActivationFunction(
+  x => (x<0)?0:x,
+  y => (x<0)?0:1
+);
+
 
 class NeuralNetwork {
   /*