Matplotlib: 带有多种颜色的y轴标签

Question

Matplotlib: 带有多种颜色的y轴标签

11

我想知道如何制作一个 y 轴标签，其中标签中的每个单词都可以是不同的颜色。

我需要这样做的原因是我将制作包含两条曲线（电场和矢势场）的图。这些曲线将是不同的颜色，我希望在标签中显示出来。以下是一个简化的示例，使用先前的帖子（Matplotlib multiple colours in tick labels）来接近答案。对于 x 轴来说，这篇文章做得很好，但它没有正确地分隔或排序 y 轴。

另一篇帖子有一个类似的问题（Partial coloring of text in matplotlib），但第一个答案似乎已经完全不起作用了，而第二个答案要求你将文件保存为 .ps 文件。

我的示例代码是：

import numpy as np 
import matplotlib.pyplot as plt
from matplotlib.offsetbox import AnchoredOffsetbox, TextArea, HPacker, VPacker

ax = plt.subplot(111)

x = np.linspace(0,10,10)
y1 = x
y2 = x**2

ax.plot(x,y1,color='r',label='data1')
ax.plot(x,y2,color='b',label='data2')
ax.set_xticks([]) # empty xticklabels
ax.set_yticks([]) # empty xticklabels

# x-axis label
xbox1 = TextArea("Data1-x ", textprops=dict(color="r", size=15))
xbox2 = TextArea("and ", textprops=dict(color="k", size=15))
xbox3 = TextArea("Data2-x ", textprops=dict(color="b", size=15))

xbox = HPacker(children=[xbox1, xbox2, xbox3],
                  align="center", pad=0, sep=5)

anchored_xbox = AnchoredOffsetbox(loc=3, child=xbox, pad=0., frameon=False,
                                      bbox_to_anchor=(0.3, -0.07),
                                      bbox_transform=ax.transAxes, borderpad=0.)

# y-axis label
ybox1 = TextArea("Data1-y ", textprops=dict(color="r", size=15,rotation='vertical'))
ybox2 = TextArea("and ", textprops=dict(color="k", size=15,rotation='vertical'))
ybox3 = TextArea("Data2-y ", textprops=dict(color="b", size=15,rotation='vertical'))

ybox = VPacker(children=[ybox1, ybox2, ybox3],
                  align="center", pad=0, sep=5)

anchored_ybox = AnchoredOffsetbox(loc=8, child=ybox, pad=0., frameon=False,
                                      bbox_to_anchor=(-0.08, 0.4),
                                      bbox_transform=ax.transAxes, borderpad=0.)


ax.add_artist(anchored_xbox)
ax.add_artist(anchored_ybox)
plt.legend()
plt.show()

感谢帮助！

- Christopher Mancuso

你有没有考虑使用 twinx()？我通常会在第二个 y 轴上绘制第二个数据集，并相应地更改颜色。 - Moritz

1个回答

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原文链接

- DanHickstein · Accepted Answer

你已经接近成功了，只需使用 ha='left',va='bottom' 指定文本的对齐方式（并且反转传递给 VPacker 的 TextArea 对象的顺序）。

import numpy as np 
import matplotlib.pyplot as plt
from matplotlib.offsetbox import AnchoredOffsetbox, TextArea, HPacker, VPacker

ax = plt.subplot(111)

x = np.linspace(0,10,10)
y1 = x
y2 = x**2

ax.plot(x,y1,color='r',label='data1')
ax.plot(x,y2,color='b',label='data2')

ybox1 = TextArea("Data2-y ", textprops=dict(color="r", size=15,rotation=90,ha='left',va='bottom'))
ybox2 = TextArea("and ",     textprops=dict(color="k", size=15,rotation=90,ha='left',va='bottom'))
ybox3 = TextArea("Data1-y ", textprops=dict(color="b", size=15,rotation=90,ha='left',va='bottom'))

ybox = VPacker(children=[ybox1, ybox2, ybox3],align="bottom", pad=0, sep=5)

anchored_ybox = AnchoredOffsetbox(loc=8, child=ybox, pad=0., frameon=False, bbox_to_anchor=(-0.08, 0.4), 
                                  bbox_transform=ax.transAxes, borderpad=0.)

ax.add_artist(anchored_ybox)
plt.legend()
plt.show()

更好的是，这里有一个函数可以使用任意字符串和颜色列表来生成标签：

import numpy as np 
import matplotlib.pyplot as plt

def multicolor_ylabel(ax,list_of_strings,list_of_colors,axis='x',anchorpad=0,**kw):
    """this function creates axes labels with multiple colors
    ax specifies the axes object where the labels should be drawn
    list_of_strings is a list of all of the text items
    list_if_colors is a corresponding list of colors for the strings
    axis='x', 'y', or 'both' and specifies which label(s) should be drawn"""
    from matplotlib.offsetbox import AnchoredOffsetbox, TextArea, HPacker, VPacker

    # x-axis label
    if axis=='x' or axis=='both':
        boxes = [TextArea(text, textprops=dict(color=color, ha='left',va='bottom',**kw)) 
                    for text,color in zip(list_of_strings,list_of_colors) ]
        xbox = HPacker(children=boxes,align="center",pad=0, sep=5)
        anchored_xbox = AnchoredOffsetbox(loc=3, child=xbox, pad=anchorpad,frameon=False,bbox_to_anchor=(0.2, -0.09),
                                          bbox_transform=ax.transAxes, borderpad=0.)
        ax.add_artist(anchored_xbox)

    # y-axis label
    if axis=='y' or axis=='both':
        boxes = [TextArea(text, textprops=dict(color=color, ha='left',va='bottom',rotation=90,**kw)) 
                     for text,color in zip(list_of_strings[::-1],list_of_colors) ]
        ybox = VPacker(children=boxes,align="center", pad=0, sep=5)
        anchored_ybox = AnchoredOffsetbox(loc=3, child=ybox, pad=anchorpad, frameon=False, bbox_to_anchor=(-0.10, 0.2), 
                                          bbox_transform=ax.transAxes, borderpad=0.)
        ax.add_artist(anchored_ybox)


ax = plt.subplot(111)

x = np.linspace(0,10,1000)
y1 = np.sin(x)
y2 = np.sin(2*x)

ax.plot(x,y1,color='r')
ax.plot(x,y2,color='b')

multicolor_ylabel(ax,('Line1','and','Line2','with','extra','colors!'),('r','k','b','k','m','g'),axis='both',size=15,weight='bold')

plt.show()

在 "bbox_to_anchor" 关键字中仍需要进行一些位置上的调整。