I don't quite understand how to control y - axis when using plt.hist plot in python. I read my .txt data file - it contains 10 columns with various data. If I want to plot distribution of strain on x axis I take column n.5. But what kind of value appears on y axis ??? Don't understand that. here is the code: import numpy import matplotlib.pyplot as plt from pylab import * from scipy.stats import norm import sys strain = [] infile = sys.argv[1] for line in infile: ret = numpy.loadtxt(infile) strain += list(ret[:,5]) fig = plt.figure() plt.hist(strain, bins = 20) plt.show() Thanks for help!