将mpatches.Patch用于自定义图例

Question

我使用以下代码来创建一个自定义matplotlib图例。

import matplotlib.patches as mpatches
import matplotlib.pyplot as plt
colors = ["g", "w"]
texts = ["Green Data Description", "RedData Description"]
patches = [ mpatches.Patch(color=colors[i], label="{:s}".format(texts[i]) ) for i in range(len(texts)) ]
plt.legend(handles=patches, bbox_to_anchor=(0.5, 0.5), loc='center', ncol=2 )

生成的图例如下：

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1-不显示图例中的白色符号，因为默认图例背景也是白色的。如何将图例背景设置为其他颜色？

2-如何将图例中的矩形符号更改为圆形？

Answer 1

1. 可以使用plt.legend()的facecolor参数设置图例的背景色。

plt.legend(facecolor="plum")

1. 要获得圆形图例手柄，可以使用带有圆形标记的标准绘图作为代理美工人员。

plt.plot([]，[]，marker="o"，ms=10，ls="")

完整示例：

import matplotlib.patches as mpatches
import matplotlib.pyplot as plt
colors = ["g", "w"]
texts = ["Green Data Description", "RedData Description"]
patches = [ plt.plot([],[], marker="o", ms=10, ls="", mec=None, color=colors[i], 
            label="{:s}".format(texts[i]) )[0]  for i in range(len(texts)) ]
plt.legend(handles=patches, bbox_to_anchor=(0.5, 0.5), 
           loc='center', ncol=2, facecolor="plum", numpoints=1 )

plt.show()

(请注意，只有旧版本的matplotlib才需要mec和numpoints参数)

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对于图例中更复杂的形状，您可以使用自定义处理程序映射，请参阅legend guide或例如this answer作为示例

Answer 2

试试这个：

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.patches as mpatches
from matplotlib.legend_handler import HandlerPatch
colors = ["g", "w"]
texts = ["Green Data Description", "RedData Description"]
class HandlerEllipse(HandlerPatch):
    def create_artists(self, legend, orig_handle,
                       xdescent, ydescent, width, height, fontsize, trans):
        center = 0.5 * width - 0.5 * xdescent, 0.5 * height - 0.5 * ydescent
        p = mpatches.Ellipse(xy=center, width=width + xdescent,
                             height=height + ydescent)
        self.update_prop(p, orig_handle, legend)
        p.set_transform(trans)
        return [p]


c = [ mpatches.Circle((0.5, 0.5), 1, facecolor=colors[i], linewidth=3) for i in range(len(texts))]
plt.legend(c,texts,bbox_to_anchor=(0.5, 0.5), loc='center', ncol=2, handler_map={mpatches.Circle: HandlerEllipse()}).get_frame().set_facecolor('#00FFCC')
plt.show()

输出：

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更新：

要循环，请在mpatches.Ellipse中将width设置为height

去掉外面的黑线，在mpatches.Circle中设置edgecolor="none"

代码：

import matplotlib.pyplot as plt
import numpy as np
import matplotlib.patches as mpatches
from matplotlib.legend_handler import HandlerPatch
colors = ["g", "w"]
texts = ["Green Data Description", "RedData Description"]
class HandlerEllipse(HandlerPatch):
    def create_artists(self, legend, orig_handle,
                       xdescent, ydescent, width, height, fontsize, trans):
        center = 0.5 * width - 0.5 * xdescent, 0.5 * height - 0.5 * ydescent
        p = mpatches.Ellipse(xy=center, width=height + xdescent,
                             height=height + ydescent)
        self.update_prop(p, orig_handle, legend)
        p.set_transform(trans)
        return [p]


c = [ mpatches.Circle((0.5, 0.5), radius = 0.25, facecolor=colors[i], edgecolor="none" ) for i in range(len(texts))]
plt.legend(c,texts,bbox_to_anchor=(0.5, 0.5), loc='center', ncol=2, handler_map={mpatches.Circle: HandlerEllipse()}).get_frame().set_facecolor('#00FFCC')
plt.show()

新图片：

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Answer 3

由于其他答案对我不起作用，我添加了一个超级简单和直接的答案：

import matplotlib.pyplot as plt
handles = []
for x in colors:
    handles.append(plt.Line2D([], [], color=x, marker="o", linewidth=0))

你可以调整标记的大小和任何你想要的东西(可能是星形等等)，线宽去掉了线条，只留下了标记。工作完美，而且超级简单！

更简单：

import matplotlib.pyplot as plt
handles = [(plt.Line2D([], [], color=x, marker="o", linewidth=0)) for x in colors]