Python: Position Text Box Fixed In Corner And Correctly Aligned

I'm trying to mimic the legend method in matplotlib.pyplot where one can use loc='lower right' to position the legend box fixed and properly aligned no matter the axis and the cont

Solution 1:

The quick-and-dirty way is to use right and top aligned text and place it at a fixed offset in points from the axes corner:

import matplotlib.pyplot as plt

# Define some names and variables to go in the text box.
xn, yn, cod = 'r', 'p', 'abc'
prec = 2
ccl = [546.35642, 6785.35416]
ect = [12.5235, 13.643241]

fig = plt.figure()
ax = fig.add_subplot(111)
ax.axis([-1, 10, -1, 1])

# Generate text to write.
text1 = "${}_{{t}} = {:.{p}f} \pm {:.{p}f}\; {c}$".format(xn, ccl[0],
    ect[0], c=cod, p=prec)
text2 = "${}_{{t}} = {:.{p}f} \pm {:.{p}f}\; {c}$".format(yn, ccl[1],
    ect[1], c=cod, p=prec)
text = text1 + '\n' + text2

ax.annotate(text, xy=(1, 1), xytext=(-15, -15), fontsize=10,
    xycoords='axes fraction', textcoords='offset points',
    bbox=dict(facecolor='white', alpha=0.8),
    horizontalalignment='right', verticalalignment='top')

plt.show()

Because we've specified top and right alignment, it works with your two edge cases:

---

The downside of this is that the text is right-aligned. Ideally, you'd want the text alignment to be separate from the box alignment. The matplotlib.offsetbox module has a number of methods to handle things like this.

If you want to mimic a legend box (down to the location codes), have a look at matplotlib.offsetbox.AnchoredText. (Note that you can adjust the padding, etc though the pad and borderpad kwargs: http://matplotlib.org/api/offsetbox_api.html#matplotlib.offsetbox.AnchoredOffsetbox )

import matplotlib.pyplot as plt
import matplotlib.offsetbox as offsetbox

# Define some names and variables to go in the text box.
xn, yn, cod = 'r', 'p', 'abc'
prec = 5
ccl = [546.35642, 6785.35416]
ect = [12.5235, 13.643241]

fig = plt.figure()
ax = fig.add_subplot(111)
ax.axis([-1, 10, -1, 1])

# Generate text to write.
text1 = "${}_{{t}} = {:.{p}f} \pm {:.{p}f}\; {c}$".format(xn, ccl[0],
    ect[0], c=cod, p=prec)
text2 = "${}_{{t}} = {:.{p}f} \pm {:.{p}f}\; {c}$".format(yn, ccl[1],
    ect[1], c=cod, p=prec)
text = text1 + '\n' + text2

ob = offsetbox.AnchoredText(text, loc=1)
ax.add_artist(ob)

plt.show()

One downside to this is that adjusting the font and box parameters for the result is a bit counter-intuitive. AnchoredText accepts a dictionary of font parameters as the prop kwarg. The box can be adjusted after initialization through the patch attribute. As a quick example:

ob = offsetbox.AnchoredText(text, loc=1,
                    prop=dict(color='white', size=20))
ob.patch.set(boxstyle='round', color='blue', alpha=0.5)
ax.add_artist(ob)