som.py

import matplotlib
matplotlib.use('Agg')

import numpy as np
from math import pi
import matplotlib.pyplot as plt

hash = {
    1: 'c',
    2: 'b',
    4: 'r',
    8: 'g',
    }

x = np.arange(0, 2, 0.001);
w = np.arange(0, 2, 1.0/8)
for key, color in hash.iteritems():
    plt.clf()
    y = np.sin(2*pi*x*key)
    z = np.sin(2*pi*w*key)
    plt.plot(x, y, color=color, label='%d MHz' % key)
    #plt.plot(w, z, 'ko')

    plt.xlabel('time (in microsecond)')
    plt.legend()

    plt.savefig('%dMHz-unsampled.png' % key)