如何在堆叠条形图的关键点设置y_ticks而不是均匀设置？

import matplotlib.pyplot as plt

# 假设有三个类别和各自的子类别数据
categories = ['Category 1', 'Category 2', 'Category 3']
subcategories = ['Subcategory 1', 'Subcategory 2', 'Subcategory 3']
values = [[10, 20, 30], [15, 25, 35], [5, 10, 15]]

# 计算每个类别的堆叠总和
totals = [sum(val) for val in values]
max_value = max(totals)

# 设置y轴刻度点的关键点
y_ticks = [0, max_value/4, max_value/2, max_value]

# 创建堆叠条形图
fig, ax = plt.subplots()
for i, val in enumerate(values):
    ax.bar(categories, val, bottom=totals[:i], label=subcategories[i])

# 设置y轴刻度点
ax.set_yticks(y_ticks)

# 添加图例和标签
ax.legend()
ax.set_xlabel('Categories')
ax.set_ylabel('Values')
ax.set_title('Stacked Bar Chart')

# 显示图表
plt.show()