Added graph for rectified linear unit

Author: mnielsen

fig/chap3/relu.png

@@ -0,0 +1,24 @@
+"""
+relu
+~~~~
+
+Plots a graph of the squashing function used by a rectified linear
+unit."""
+
+import numpy as np
+import matplotlib.pyplot as plt
+
+z = np.arange(-2, 2, .1)
+zero = np.zeros(len(z))
+y = np.max([zero, z], axis=0)
+
+fig = plt.figure()
+ax = fig.add_subplot(111)
+ax.plot(z, y)
+ax.set_ylim([-2.0, 2.0])
+ax.set_xlim([-2.0, 2.0])
+ax.grid(True)
+ax.set_xlabel('z')
+ax.set_title('Rectified linear unit')
+
+plt.show()