How to plot data from multiple two column text files with legends in Matplotlib?

Question

How do I open multiple text files from different directories and plot them on a single graph with legends?

Answer 1

This is relatively simple if you use pylab (included with matplotlib) instead of matplotlib directly. Start off with a list of filenames and legend names, like [ ('name of file 1', 'label 1'), ('name of file 2', 'label 2'), ...]. Then you can use something like the following:

import pylab  datalist = [ ( pylab.loadtxt(filename), label ) for filename, label in list_of_files ]  for data, label in datalist:     pylab.plot( data[:,0], data[:,1], label=label )  pylab.legend() pylab.title("Title of Plot") pylab.xlabel("X Axis Label") pylab.ylabel("Y Axis Label") 

You also might want to add something like fmt='o' to the plot command, in order to change from a line to points. By default, matplotlib with pylab plots onto the same figure without clearing it, so you can just run the plot command multiple times.