使用Matplotlib绘制图例样式中的离散颜色条

Question

有时，我想在pcolormesh样式中绘制离散值。

例如，表示形状为100x100的二维数组，其中包含int 0~7

data  = np.random.randint(8, size=(100,100))
cmap = plt.cm.get_cmap('PiYG', 8) 
plt.pcolormesh(data,cmap = cmap,alpha = 0.75)
plt.colorbar()  

图中显示如下：

如何以图例样式生成颜色条。换句话说，每个颜色框对应于其值（例如粉红色颜色框 - > 0）

此处的插图（不适合此示例）：

Answer 1

也许最简单的方法是创建相应数量的Patch实例：

import matplotlib.patches as mpatches
import matplotlib.pyplot as plt
import numpy as np

data  = np.random.randint(8, size=(100,100))
cmap = plt.cm.get_cmap('PiYG', 8) 
plt.pcolormesh(data,cmap = cmap,alpha = 0.75)
# Set borders in the interval [0, 1]
bound = np.linspace(0, 1, 9)
# Preparing borders for the legend
bound_prep = np.round(bound * 7, 2)
# Creating 8 Patch instances
plt.legend([mpatches.Patch(color=cmap(b)) for b in bound[:-1]],
           ['{} - {}'.format(bound_prep[i], bound_prep[i+1] - 0.01) for i in range(8)])