from mlxtend.plotting import plot_decision_regions
def knn_comparision(data, k):
X = data[['x1','x2']].values
y = data['y'].astype(int).values
clf = neighbors.KNeighborsClassifier(n_neighbors=k)
clf.fit(X, y)
# Plotting decision regions
plot_decision_regions(X, y, clf=clf, legend=2)
plot_decision_regions中的参数“ clf ”和“ legend ”是什么?