python - Matplotlib xy 线图图例

Question

如何在 IPython 笔记本内的 Matplotlib 中向 xy 线图添加图例？我目前的尝试:

x = np.linspace(0, 3*np.pi, 500)
a = plt.plot(x, np.sin(x**2))
b = plt.plot(x, np.sin(x**0.5))
plt.legend([a,b], ['square', 'square root'])

这样做时，我收到以下错误:

/Users/mc/.virtualenvs/kaggle/lib/python2.7/site-packages/matplotlib/legend.py:613: UserWarning: Legend does not support [] Use proxy artist instead.

http://matplotlib.sourceforge.net/users/legend_guide.html#using-proxy-artist

(str(orig_handle),)) /Users/mc/.virtualenvs/kaggle/lib/python2.7/site-packages/matplotlib/legend.py:613: UserWarning: Legend does not support [] Use proxy artist instead.

http://matplotlib.sourceforge.net/users/legend_guide.html#using-proxy-artist

(str(orig_handle),))

如果我执行 plt.scatter 而不是 plt.plot，则此命令有效，但我想要一个折线图而不是 x,y 点。

Answer 1

这样做怎么样？

x = np.linspace(0, 3*np.pi, 500)
fig, ax = plt.subplots()
a = ax.plot(x, np.sin(x**2), label = 'square')
b = ax.plot(x, np.sin(x**0.5), label = 'square root')
handles, labels = ax.get_legend_handles_labels()
ax.legend(handles, labels)

要得到这个: