python - Plot with non-numerical data on x axis (for ex., dates)

Question

I'd like to plot numerical data against non numerical data, say something like this:

import matplotlib.pyplot as pl
x=['a','b','c','d']
y=[1,2,3,4]
pl.plot(x,y)

However, with matplotlib plot packages you get a warning that the data is not float (ValueError: invalid literal for float(): a).

In their 'How-to', they suggest to put first the numerical data on the x axis and then format it. Is there a way to do it directly (as above)?

Answer 1

Use the xticks function.

import matplotlib.pyplot as pl
xticks=['a','b','c','d']
x=[1,2,3,4]
y=[1,2,3,4]
pl.plot(x,y)
pl.xticks(x,xticks)
pl.show()