from matplotlib.colors import ListedColormap
import matplotlib.pyplot as plt
def plot_decision_regions(X,y, classifier, test_idx=None, 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], label=cl, edgecolor='black', marker=markers[idx])