File:Mplwp shannon entropy.svg

#!/usr/bin/python
# -*- coding: utf8 -*-

import matplotlib.pyplot as plt
import matplotlib as mpl
import numpy as np
from math import *

code_website = 'http://commons.wikimedia.org/wiki/User:Geek3/mplwp'
try:
    import mplwp
except ImportError, er:
    print 'ImportError:', er
    print 'You need to download mplwp.py from', code_website
    exit(1)

name = 'mplwp_shannon_entropy.svg'
fig = mplwp.fig_standard(mpl)

xlim = 0, 1; fig.gca().set_xlim(xlim)
ylim = 0, 1.2; fig.gca().set_ylim(ylim)
mplwp.mark_axeszero(fig.gca())

x = np.linspace(0, 1, 5001)
def f(x):
    if x == 0 or x == 1: return 0
    return (x * log(x) + (1-x) * log(1-x)) / log(0.5)
y = [f(xx) for xx in x]
plt.plot(x, y, label=ur'$\sum_{p=x,1\u2212x}\u2212p\cdot\,log_2(p)$')

plt.legend(loc='lower center').get_frame().set_alpha(0.9)
plt.savefig(name)
mplwp.postprocess(name)