[FIXED] how to set legend to a matplolib Axes in a subfigure plot

Issue

I am trying to plot the decision boundary of an SVM classifier using iris dataset. The class label doesn't appear on the legend although I set label=y.

Code:

import matplotlib.pyplot as plt 
from sklearn import svm, datasets 
from sklearn.inspection import DecisionBoundaryDisplay

iris = datasets.load_iris()
X = iris.data[:, :2]
y = iris.target

linear = svm.LinearSVC()
linear.fit(X,y)

X0, X1 = X[:, 0], X[:, 1]

fig, ax = plt.subplots(figsize=(10, 6))
disp = DecisionBoundaryDisplay.from_estimator(linear, X,
    response_method='predict',cmap=plt.cm.coolwarm, alpha=.8,ax=ax,
    xlabel=iris.feature_names[0],ylabel=iris.feature_names[1],label=y)
ax.scatter(X0, X1, c=y, cmap=plt.cm.coolwarm, s=20, edgecolors='k')
ax.set_xticks(())
ax.set_yticks(())
ax.set_title('Some title') 
ax.legend()
plt.show()

Figure:

Solution

U could use automatic legend creation. In your case:

scatter = ax.scatter(X0, X1, c=y, cmap=plt.cm.coolwarm, s=20, edgecolors='k',
           )
legend1 = ax.legend(*scatter.legend_elements(),
                    loc="lower left", title="Classes")
ax.add_artist(legend1)

Which produces:

Answered By - arilwan