如何用颜色填充对数螺线

Question

我写了一段画对数螺线的代码，现在曲线画好了，但是对于颜色填充部分，我不熟悉如何填充它（两条曲线之间的部分，和之间的部分曲线和外圆边界）。填色部分如何完成？ fill_between这里更合适吗？

import matplotlib.pyplot as plt
b = 0.2
a = 2

theta = np.linspace(0, np.pi * 3.0, 1000, endpoint=True)


r = exp(b * theta) * a

theta0 = np.linspace(0, np.pi * 4.0, 1000, endpoint=True)
r0 = [r[-1]] * len(theta0)


theta2 = np.linspace(np.pi, np.pi * 4.0, 1000, endpoint=True)
r2 = exp(b * theta) * a

ax = plt.subplot(111, projection='polar')

ax.set_rmax(r[-1])
ax.fill(theta0, r0, c='blue')
ax.plot(theta, r)

ax.plot(theta2, r2)
ax.fill(theta2, r2, 'red')


theta3 = np.linspace(0, np.pi * 2.0, 1000, endpoint=True)
r3 = [a] * len(theta3)

plt.box(on=None)
ax.fill(theta3, r3, c='black')

ax.grid(False)
plt.show()

我现在得到的是：

Answer 1

一种方法是为填充命令创建一条闭合线，将不同的部分放在一起：

import matplotlib.pyplot as plt
import numpy as np

b = 0.2
a = 2

theta1 = np.linspace(0, np.pi * 3.0, 1000, endpoint=True)
r1 = np.exp(b * theta1) * a
theta2 = np.linspace(np.pi, np.pi * 4.0, 1000, endpoint=True)
r2 = np.exp(b * theta1) * a
theta3 = np.linspace(np.pi, 0, 1000)
r3 = r1[-1] * np.ones_like(theta3)
theta4 = np.linspace(np.pi, 2 * np.pi, 1000)
r4 = a * np.ones_like(theta4)
theta5 = np.linspace(np.pi, 2*np.pi, 1000)
r5 = r1[-1] * np.ones_like(theta5)
theta6 = np.linspace(0, np.pi, 1000)
r6 = a * np.ones_like(theta6)

# put together the different pieces
theta_final_red = np.concatenate([theta1, theta3, np.flip(theta2), theta4])
radius_red = np.concatenate([r1, r3, np.flip(r2), r4])
theta_final_blue = np.concatenate([theta1, theta5, np.flip(theta2), theta6])
radius_blue = np.concatenate([r1, r5, np.flip(r2), r6])

fig = plt.figure()
ax = fig.add_subplot(111, projection='polar')
ax.set_rmax(r1[-1])

ax.fill(theta_final_red, radius_red, "r")
ax.fill(theta_final_blue, radius_blue, "b")
ax.plot(theta1, r1)
ax.plot(theta2, r2)

# black inner circle
theta3 = np.linspace(0, np.pi * 2.0, 1000, endpoint=True)
r3 = [a] * len(theta3)
ax.fill(theta3, r3, c='black')
ax.axis(False)
ax.grid(False)
plt.show()

如何用颜色填充对数螺线

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