使用matplotlib在图中绘制圆

Question

I have a graph plot and now I need a circle on it for every point where y equals zero. The graph works fine but the circle (code in the if statement) gives an error:

import numpy as np
import matplotlib.pyplot as plt


def graph(formula, x_range):
    x = np.array(x_range)
    y = formula(x)  # <-----
    #if x == y:
    if y == 0:
        circle2=plt.Circle((x,y),.2,color='b')
        fig = plt.gcf()
        fig.gca().add_artist(circle2)
        plt.show()
    plt.plot(x, y, 'r--')
    plt.show()

graph(lambda x: (x+2) * (x-1) * (x-2), range(-3,3))

Answer 1

You're passing an array x , y . Pass a single values.

def graph(formula, x_range):
    x = np.array(x_range)
    y = formula(x)
    for x0, y0 in zip(x, y):
        if y0 == 0:
            circle2 = plt.Circle((x0, y0), 0.1, color='b')  # <------
            fig = plt.gcf()
            fig.gca().add_artist(circle2)
    plt.plot(x, y, 'r--')
    plt.show()