Python 使用 pandas 和 matplotlib.pyplot 创建图例
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Create a legend with pandas and matplotlib.pyplot
提问by paco_uk
This is my first attempt at plotting with python and I'm having problems creating a legend.
这是我第一次尝试用 python 绘图，但我在创建图例时遇到了问题。
These are my imports:
这些是我的进口：
import matplotlib.pyplot as plt
import pandas
I load my data like this:
我像这样加载我的数据：
data = pandas.read_csv( 'data/output/limits.dat', sep=r"\s+", encoding = 'utf-8' )
and plot it like this:
并像这样绘制它：
axdata = data.plot( label = '$|U|^{2}$' , x = 'mass', y = 'U2',
style = '-s', markeredgecolor = 'none' )
Apparently axdata is now an AxesSubplot.
显然 axdata 现在是一个 AxesSubplot.
Now I want to create a legend as described herelike this:
现在我想像这里描述的那样创建一个图例：
plt.legend( (line1), ('label1') )
but I don't know how to extract a lineobject from an AxesSubplot
但我不知道如何line从一个对象中提取一个对象AxesSubplot
plt.legend()on its own works, but I only want some of my lines to feature in the legend. Is this the right approach? Is there another command I can use here?
plt.legend()在它自己的作品中，但我只希望我的一些台词出现在图例中。这是正确的方法吗？我可以在这里使用另一个命令吗？
EDIT:
编辑：
For example, if I try:
例如，如果我尝试：
plt.legend( [axdata], ['U2'])
I get the error:
我收到错误：
~/.virtualenvs/science/lib/python3.3/site-packages/matplotlib/legend.py:613:
UserWarning: Legend does not support Axes(0.125,0.1;0.775x0.8)
Use proxy artist instead.
http://matplotlib.sourceforge.net/users/legend_guide.html#using-proxy-artist
(str(orig_handle),))
I haven't worked out what a proxy artist is yet but I think it is a tool for when you are using a non-default graphical object, which I thought probably was not the case here because I am trying to produce a normal matlibplot plot. The words 'non-default' and 'normal' are mine - I'm not sure what they mean yet.
我还没有弄清楚代理艺术家是什么，但我认为它是当您使用非默认图形对象时的一种工具，我认为这里可能不是这种情况，因为我正在尝试生成一个正常的 matlibplot 图. “非默认”和“正常”这两个词是我的意思——我还不确定它们是什么意思。
ANOTHER EDIT:(because I misread the comment )
另一个编辑：（因为我误读了评论）
plt.legend()on it's own doesn't output anything to the console but the resulting plot now has a legend auto-generated from the plotted data.
plt.legend()它本身不会向控制台输出任何内容，但结果图现在具有从绘制数据自动生成的图例。
采纳答案by jmz
I think what you want to do is be able to display a legend for a subset of the lines on your plot. This should do it:
我认为您想要做的是能够为您的情节中的一部分线显示图例。这应该这样做：
df = pd.DataFrame(np.random.randn(400, 4), columns=['one', 'two', 'three', 'four'])
ax1 = df.cumsum().plot()
lines, labels = ax1.get_legend_handles_labels()
ax1.legend(lines[:2], labels[:2], loc='best') # legend for first two lines only
Giving
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