python - 将图例添加到 LineCollection 图中

Question

这是与Set line colors according to colormap中给出的答案相关的派生问题其中提出了一个很好的解决方案，即根据颜色条绘制多 strip 有颜色的线条(请参见下面的代码和输出图像)。

我有一个列表，其中存储了与每条标绘线关联的字符串，如下所示:

legend_list = ['line_1', 'line_2', 'line_3', 'line_4']

我想将这些字符串作为图例添加到绘图右上角的框中(其中第一个字符串对应于第一条绘制线等)。我怎么能这样做？

如果有必要，我愿意不使用 LineCollection，但我需要保持颜色条和与其关联的每条线的颜色。

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代码和输出

import numpy
import matplotlib.pyplot as plt
from matplotlib.collections import LineCollection

# The line format you curently have:
lines = [[(0, 1, 2, 3, 4), (4, 5, 6, 7, 8)],
         [(0, 1, 2, 3, 4), (0, 1, 2, 3, 4)],
         [(0, 1, 2, 3, 4), (8, 7, 6, 5, 4)],
         [(4, 5, 6, 7, 8), (0, 1, 2, 3, 4)]]

# Reformat it to what `LineCollection` expects:
lines = [zip(x, y) for x, y in lines]

z = np.array([0.1, 9.4, 3.8, 2.0])

fig, ax = plt.subplots()
lines = LineCollection(lines, array=z, cmap=plt.cm.rainbow, linewidths=5)
ax.add_collection(lines)
fig.colorbar(lines)

# Manually adding artists doesn't rescale the plot, so we need to autoscale
ax.autoscale()

plt.show()

Answer 1

如果您的行数较少，@unutbu 的回答是正确的方法。 (如果您想添加图例，您大概会这样做!)

只是为了显示另一个选项，您仍然可以使用 LineCollection，您只需要为图例使用“代理艺术家”:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.collections import LineCollection
from matplotlib.lines import Line2D

# The line format you curently have:
lines = [[(0, 1, 2, 3, 4), (4, 5, 6, 7, 8)],
         [(0, 1, 2, 3, 4), (0, 1, 2, 3, 4)],
         [(0, 1, 2, 3, 4), (8, 7, 6, 5, 4)],
         [(4, 5, 6, 7, 8), (0, 1, 2, 3, 4)]]

# Reformat it to what `LineCollection` expects:
lines = [tuple(zip(x, y)) for x, y in lines]

z = np.array([0.1, 9.4, 3.8, 2.0])

fig, ax = plt.subplots()
lines = LineCollection(lines, array=z, linewidths=5,
                       cmap=plt.cm.rainbow, norm=plt.Normalize(z.min(), z.max()))
ax.add_collection(lines)
fig.colorbar(lines)

# Manually adding artists doesn't rescale the plot, so we need to autoscale
ax.autoscale()

def make_proxy(zvalue, scalar_mappable, **kwargs):
    color = scalar_mappable.cmap(scalar_mappable.norm(zvalue))
    return Line2D([0, 1], [0, 1], color=color, **kwargs)
proxies = [make_proxy(item, lines, linewidth=5) for item in z]
ax.legend(proxies, ['Line 1', 'Line 2', 'Line 3', 'Line 4'])

plt.show()