Force integer axis labels on Matplotlib

March 24, 2021

To make a Matlabplot figure axis have integer-only labels, use method like:

ax.yaxis.set_major_locator(MaxNLocator(integer=True))
# or
ax.xaxis.set_major_locator(MaxNLocator(integer=True))

A complete standalone example follows:

import numpy as np
from matplotlib.figure import Figure
from matplotlib.ticker import MaxNLocator

x = np.arange(0.1,10.5,0.1) # arbitrary data

fg = Figure()
ax = fg.gca()
ax.plot(x)

ax.yaxis.set_major_locator(MaxNLocator(integer=True))

fg.savefig("example.png")

If too few ticks are displayed, as per the Matplotlib MaxNLocator, you must have “at least min_n_ticks integers…found within the view limits.” Set “MaxNLocator(nbins=5,integer=True)” or similar if the defaults aren’t forcing integer ticks.