Plot x,y pairs from csv file.

plot_csv.py

"""
Plot x,y pairs from csv file.

usage:

    python plot_csv.py xy_data.csv

csv format:

    assume no header row
    assume rows are form "123.0,456.0\n" etc
"""

import csv
import pylab # see http://matplotlib.sourceforge.net/
import sys

def main():
    if len(sys.argv) != 2:
        print 'usage: python plot_csv.py xy_data.csv'
        sys.exit(1)

    xs = []
    ys = []
    with open(sys.argv[1], 'r') as f:
        reader = csv.reader(f, delimiter = ',')
        for row in reader:
            xs.append(float(row[0]))
            ys.append(float(row[1]))

    pylab.figure()
    pylab.title('x versus y : the final reckoning')
    pylab.scatter(xs, ys, label = 'extremely helpful data points')
    pylab.legend(loc = 'upper left')
    pylab.xlabel('x')
    pylab.ylabel('y')
    pylab.show() # delete this to run in batch mode (saving many figs etc)
    # you can save em too
    # pylab.savefig('plot.png')

if __name__ == '__main__':
    main()