使用极坐标绘制螺旋线（projection='polar'）并在图中标记文本和注释

以下是使用 Matplotlib 绘制极坐标螺旋线的示例代码，其中包括添加标签和注释：

import numpy as np
import matplotlib.pyplot as plt

# 构造数据
theta = np.linspace(0, 10 * np.pi, 1000)
r = np.exp(0.3 * theta)

# 绘制极坐标螺旋线
fig = plt.figure()
ax = fig.add_subplot(111, projection='polar')
ax.plot(theta, r)

# 添加文本标签
ax.text(0, 0, 'O', ha='center', va='center')
ax.text(np.pi / 2, np.exp(0.3 * np.pi / 2), 'A', ha='center', va='bottom')
ax.text(np.pi, np.exp(0.3 * np.pi), 'B', ha='center', va='top')
ax.text(3 * np.pi / 2, np.exp(0.3 * 3 * np.pi / 2), 'C', ha='center', va='bottom')

# 添加注释
ax.annotate('Origin', xy=(0, 0), xytext=(np.pi / 4, 1.2),
            arrowprops=dict(facecolor='black', shrink=0.05))
ax.annotate('Increase in r', xy=(np.pi / 2, np.exp(0.3 * np.pi / 2)), xytext=(np.pi / 2, 2),
            arrowprops=dict(facecolor='black', shrink=0.05))
ax.annotate('Increase in theta', xy=(np.pi, np.exp(0.3 * np.pi)), xytext=(3 * np.pi / 4, 1.2),
            arrowprops=dict(facecolor='black', shrink=0.05))
ax.annotate('Increase in r and theta', xy=(3 * np.pi / 2, np.exp(0.3 * 3 * np.pi / 2)), xytext=(5 * np.pi / 4, 1.2),
            arrowprops=dict(facecolor='black', shrink=0.05))

# 显示图形
plt.show()

运行代码后会生成一个带有文本标签和注释的极坐标螺旋线图形。注释可以帮助读者更好地理解图形中各个元素的含义。