跟着老师打的，可是为什么会报错NameError: name 'X' is not defined？

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

    x1_min,x1_max = X[:,0].min() - 1, X[:,0].max()
    x2_min,x2_max = X[:,1].min() - 1, X[:,1].max()

    print(x1_min,x1_max)
    print(x2_min,x2_max)


plot_decision_regions(X, y, ppn, resolution=0.02)

Traceback (most recent call last):

  File "E:/python/pythonproject/robot_learning/test.py", line 100, in <module>

    plot_decision_regions(X, y, ppn, resolution=0.02)

NameError: name 'X' is not defined