Matplotlib 动画：图形无法出现

Question

最近我设法做了动画。但是现在我不能让切线按照我的意愿走（甚至还没有显示）。切线的公式为y=(2/r)(sqrt(1-((r^2)/4))-1)x +r。该公式是从 2 个圆方程（C1 和 C2）中获得的。 C1（蓝色）：x^2+y^2=r^2，C2（绿色）：（x-1）^2+y^2=1。我的目标是获得这种动画为，而我当前的动画是这样的。

当动画看起来像参考动画（第一个）时，代码应该如何？作为初学者，任何cmets和答案都会对我非常有帮助，我很感激，谢谢。

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation

fig, ax = plt.subplots(1)
line, = ax.plot([], [], lw=2)
line2, = ax.plot([], [], lw=2)
ax.set_xlim(-5,5)
ax.set_ylim(-5,5)
# theta goes from 0 to 2pi
theta = np.linspace(0, 2*np.pi, 100)

# the radius of the circle
r = np.sqrt(1)
r2 = np.sqrt(4)

# compute x1 and x2
x1 = 1+r*np.cos(theta)
y1 = r*np.sin(theta)
x2 = r2*np.cos(theta)
y2 = r2*np.sin(theta)

# Move left y-axis and bottim x-axis to centre, passing through (0,0)
ax.spines['left'].set_position('center')
ax.spines['bottom'].set_position('center')

# Eliminate upper and right axes
ax.spines['right'].set_color('none')
ax.spines['top'].set_color('none')

# Show ticks in the left and lower axes only
ax.xaxis.set_ticks_position('bottom')
ax.yaxis.set_ticks_position('left')

def init():
    line.set_data([], [])
    return line,
def init2():
    line.set_data([], [])
    return line2,
def animate(i):
    x2 = np.sqrt(i)*np.cos(theta)
    y2 = np.sqrt(i)*np.sin(theta)
    line.set_data(x2, y2)
    return line,
def animate2(i):
    x3 = np.linspace(0,r2**2,100)
    y3 = ((2/r2)*(np.sqrt(1-(r2**2)/4)-1)*x3)+r2
    line.set_data(x3, y3)
    return line,

# create the figure
ax.plot(x1,y1)
ax.set_aspect(1)
plt.grid()
anim = animation.FuncAnimation(fig, animate, init_func=init,
                                interval=1000, blit=False,\
                                frames=np.hstack([range(0), 
                                                  range(4)[::-1]]))
anim2 = animation.FuncAnimation(fig, animate2, init_func=init2,
                                interval=1000, blit=False)
                                
plt.show()

f = r"D:/UNPAR/Semester 2/Pemrograman Komputer/Project/SK.gif" 
writergif = animation.PillowWriter(fps=30) 
anim.save(f, writer=writergif)

Answer 1

动画功能需要合二为一。我们将它们组合成一个初始化函数和一个动画函数。

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation

fig, ax = plt.subplots(1)
line, = ax.plot([], [], lw=2, color='green')
line2, = ax.plot([], [], lw=2, color='red')
ax.set_xlim(-5,5)
ax.set_ylim(-5,5)

# theta goes from 0 to 2pi
theta = np.linspace(0, 2*np.pi, 100)

# the radius of the circle
r = np.sqrt(1)
r2 = np.sqrt(4)

# compute x1 and x2
x1 = 1+r*np.cos(theta)
y1 = r*np.sin(theta)
x2 = r2*np.cos(theta)
y2 = r2*np.sin(theta)

# create the figure
ax.plot(x1,y1)
ax.set_aspect(1)
plt.grid()

def init():
    line.set_data([], [])
    line2.set_data([], [])
    return line,line2

def animate(i):
    x2 = np.sqrt(i)*np.cos(theta)
    y2 = np.sqrt(i)*np.sin(theta)
    print(max(y2))
    line.set_data(x2, y2)

    x3 = [0, 4-(0.1*i)]
    y3 = [max(y2), 0]
    line2.set_data(x3, y3)    
    return line,line2


anim = animation.FuncAnimation(fig, animate, init_func=init, interval=1000, blit=False,frames=np.arange(10,0,-1))
                 
plt.show()