Subscripting text in matplotlib labels

Question

this is my first question and I am a noob at python. So probably more to follow...

I would like to create a figure with matplotlib. In the labels, I would like to include a chemical formula, which involves subscripts (I think the same would work for superscripts...).

Anyway, I have no idea, how the label would have to look like.

import numpy as nu
import pylab as plt

x = nu.array([1,2,3,4])
y = nu.array([1,2,3,4])

plt.plot(x,y, label='H2O')
plt.legend(loc=1)
plt.show()

Ok, this gives me a plot with the label "H2O". How can I subscript the "2" in the label, as is common for chemical formulae?

I searched the web, but I didn't find anything useful yet.

I figured that I could use

from matplotlib import rc
rc['text', usetex=True]

but I don't want to use it (I know how to use LaTeX, but I don't want here).

Another option is:

label='H$_2$O'

but this changes the font (math).

There MUST be a way, how does subscripting in matplotlib-legends work?

Thanks a lot!

fernandezr · Accepted Answer · 2013-06-16 23:32:16Z

5

Try to change this line

plt.plot(x,y, label='H2O')

for this:

plt.plot(x,y, label='$H_2O$')

It shows with the font math.

Or also you can use the unicode character for that: ₂ (0xE2 / ₂)

plt.plot(x,y, label=u'H₂O')

or instead:

plt.plot(x,y, label=u"H\u2082O")

Please, note that unicode strings are noted as u"" instead than "".

edited Jun 16, 2013 at 23:32

answered Jun 16, 2013 at 23:01

fernandezr

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7 Comments

SKchem Over a year ago

thanks, I already tried this (in the meantime). It returns in a different style than lables etc... Is there really no simple way without changing the style?

SKchem Over a year ago

label=u'H\2082O' returns something weird... Sorry, I have no idea how to use unicode here...in your code line, the "2" is somewhat smaller ans subscripted, how did you do this?

fernandezr Over a year ago

Simply copy the line. Anyway, I got this looking on charmap utility (I'm on linux, but under Windows should works too. It has a charmap)

SKchem Over a year ago

yes, I copied. But it returns a box for the subscripted "2"... I added # -- coding: utf-8 -- but it remains the same. Something with the font?

fernandezr Over a year ago

Other solution is using that (i just discovered): u"\u2082". This returns a subscript 2

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