Jay Gattuso Jay Gattuso - 5 months ago 24
Python Question

Force the Y axis to only use integers

I'm plotting a histogram using the matplotlib.pyplot module and I am wondering how I can force the y-axis labels to only show integers (e.g. 0, 1, 2, 3 etc.) and not decimals (e.g. 0., 0.5, 1., 1.5, 2. etc.).

I'm looking at the guidance notes and suspect the answer lies somewhere around matplotlib.pyplot.ylim but so far I can only find stuff that sets the minimum and maximum y-axis values.

def doMakeChart(item, x):
if len(x)==1:
return
filename = "C:\Users\me\maxbyte3\charts\\"
bins=logspace(0.1, 10, 100)
plt.hist(x, bins=bins, facecolor='green', alpha=0.75)
plt.gca().set_xscale("log")
plt.xlabel('Size (Bytes)')
plt.ylabel('Count')
plt.suptitle(r'Normal Distribution for Set of Files')
plt.title('Reference PUID: %s' % item)
plt.grid(True)
plt.savefig(filename + item + '.png')
plt.clf()

Answer

If you have the y-data

y = [0., 0.5, 1., 1.5, 2., 2.5]

You can use the maximum and minimum values of this data to create a list of natural numbers in this range. For example,

import math
print range(math.floor(min(y)), math.ceil(max(y))+1)

yields

[0, 1, 2, 3]

You can then set the y tick mark locations (and labels) using matplotlib.pyplot.yticks:

yint = range(min(y), math.ceil(max(y))+1)

matplotlib.pyplot.yticks(yint)