如何创建中间有零线的多因素水平比例条形图？

import matplotlib.pyplot as plt
import numpy as np

# 示例数据
categories = ['A', 'B', 'C', 'D']
values1 = [10, -15, 20, -5]
values2 = [-8, 12, -18, 6]

# 设置条形图的位置
bar_width = 0.35
index = np.arange(len(categories))

# 创建图形和轴
fig, ax = plt.subplots()

# 绘制条形图
bar1 = ax.barh(index, values1, bar_width, label='Factor 1', color='skyblue')
bar2 = ax.barh(index + bar_width, values2, bar_width, label='Factor 2', color='lightgreen')

# 添加零线
ax.axvline(0, color='black', linewidth=1)

# 设置轴标签和标题
ax.set_xlabel('Values')
ax.set_ylabel('Categories')
ax.set_title('Multi-Factor Horizontal Proportional Bar Chart with Zero Line')
ax.set_yticks(index + bar_width / 2)
ax.set_yticklabels(categories)

# 添加图例
ax.legend()

# 显示图形
plt.show()