from matplotlib.colors import ListedColormap
import numpy as np
import matplotlib.pyplot as plt

def plot_decision_regions(X, y, classifier, resolution=0.02):
    markers = ('s','x','o','^','v')
    colors=('red','blue','lightgreen','gray','cyan')
    cmap=ListedColormap(colors[:len(np.unique(y))])

    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=0.3, cmap=cmap)
    plt.xlim(xx1.min(),xx1.max())
    plt.ylim(xx2.min(),xx2.max())

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