pdr.py

import numpy as np
import matplotlib.pyplot as plt 

from matplotlib.colors import ListedColormap

""" Function to color the deciosion regions """

def plot_decision_regions(X, y, classifier, resolution = 0.02):

	# setup marker generator and color map

	markers = ('s', 'x', 'o', '^', 'v')
	colors = ('red', 'blue', 'lightgreen', 'gray', 'cyan')
	cmap = ListedColormap(colors[ : len(np.unique(y))])

	# plot the decision surface

	x1_min, x1_max = X[:, 0].min() - 1, X[:, 0].max() + 1
	x2_min, x2_max = X[:, 1].min() - 1, X[:, 1].max() + 1
	xx1, xx2 = np.meshgrid(np.arange(x1_min, x1_max, resolution),
		np.arange(x2_min, x2_max, resolution))

	z = classifier.predict(np.array([xx1.ravel(), xx2.ravel()]).T)
	Z = z.reshape(xx1.shape)

	plt.contourf(xx1, xx2, Z, alpha = 0.4, cmap = cmap)
	plt.xlim(xx1.min(), xx1.max())
	plt.ylim(xx2.min(), xx2.max())

	# plot class samples

	for idx, cl in enumerate(np.unique(y)):
		plt.scatter(x = X[y == cl, 0], y = X[y == cl, 1],
			alpha = 0.8, c = cmap(idx), marker = markers[idx],
			label = cl)