Question

I’m having trouble changing the tick label properties on a plot with twin axes. I want the text to be small and in a different font than the default. I found a way that worked fine until I tried using twiny(). The second axes doesn’t respond to the tick-formatting instructions, as you can see on the figure. Am I missing something crucial or is there a bug in matplotlib?

Ubuntu 12.04, Python 2.7.3, matplotlib 1.1.1rc

#!/usr/bin/env python
# coding: utf-8

from matplotlib import pyplot as p
from numpy import sin, cos, arange

x = arange(0, 10, .01)

for plotnum in range(1,5):
    p.subplot(2, 2, plotnum)
    ax1 = p.gca()
    p.plot(sin(x),x)
    ax2 = p.twiny()
    p.plot(cos(x)+plotnum,x, 'g--')

    # Set size all tick labels
    # Works for first axes (lower x-ticks) and can also change font
    for tickset in [ax1.xaxis.get_major_ticks()]:
        [(tick.label.set_fontsize(plotnum*4), tick.label.set_fontname('ubuntu mono')) for tick in tickset]

    # Does not work for second axes (upper x-ticks)
    for tickset in [ax2.xaxis.get_major_ticks()]:
        [(tick.label.set_fontsize(plotnum*2), tick.label.set_fontname('ubuntu mono')) for tick in tickset]

    # This works, but doesn't allow changing font
    #ax2.tick_params(axis='both', which='major', labelsize=plotnum*2)

Here is an image:

Edit: fixed incorrect indenting of tick-changing lines

Edit: Inserted image (Thriveth)

Answer 1

Ticks can have two labels (label1 and label2), according to the Tick class documentation:

• 1 refers to the bottom of the plot for xticks and the left for yticks
• 2 refers to the top of the plot for xticks and the right for yticks

The label attribute always refers to label1.

You can fix your script by changing the ax2 lines to:

for tickset in [ax2.xaxis.get_major_ticks()]:
    [(tick.label2.set_fontsize(plotnum*2), tick.label2.set_fontname('ubuntu mono'))

The get_majorticklabels functions will work out if you ‘ll need label1 or label2 and simplifies your script:

from matplotlib import pyplot as p
from numpy import sin, cos, arange

x = arange(0, 10, .01)

for plotnum in range(1,5):
    p.subplot(2, 2, plotnum)
    ax1 = p.gca()
    p.plot(sin(x),x)
    ax2 = p.twiny()
    p.plot(cos(x)+plotnum,x, 'g--')
    for label in ax1.xaxis.get_majorticklabels():
        label.set_fontsize(plotnum * 4)
        label.set_fontname('courier')
    for label in ax2.xaxis.get_majorticklabels():
        label.set_fontsize(plotnum * 4)
        label.set_fontname('verdana')

Note, I put the label change routines in the loop!