automatically position text box in matplotlib

问题:

Is there a way of telling pyplot.text() a location like you can with pyplot.legend()?

Something like the legend argument would be excellent:

plt.legend(loc="upper left")

I am trying to label subplots with different axes using letters (e.g. "A","B"). I figure there's got to be a better way than manually estimating the position.

Thanks

回答1:

Just use annotate and specify axis coordinates. For example, "upper left" would be:

plt.annotate('Something', xy=(0.05, 0.95), xycoords='axes fraction')

You could also get fancier and specify a constant offset in points:

plt.annotate('Something', xy=(0, 1), xytext=(12, -12), va='top'
             xycoords='axes fraction', textcoords='offset points')

For more explanation see the examples here and the more detailed examples here.

回答2:

I'm not sure if this was available when I originally posted the question but using the loc parameter can now actually be used. Below is an example:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib.offsetbox import AnchoredText

# make some data
x = np.arange(10)
y = x

# set up figure and axes
f, ax = plt.subplots(1,1)

# loc works the same as it does with figures (though best doesn't work)
# pad=5 will increase the size of padding between the border and text
# borderpad=5 will increase the distance between the border and the axes
# frameon=False will remove the box around the text

anchored_text = AnchoredText("Test", loc=2)
ax.plot(x,y)
ax.add_artist(anchored_text)

plt.show()