bgneal@30: """Chapter 5.3 exercise 4 in Allen Downey's Think Complexity book.
bgneal@30: 
bgneal@30: "Write a version of plot_ccdf that plots the complementary CCDF on a log-log
bgneal@30: scale.
bgneal@30: 
bgneal@30: To test your function, use paretovariate from the random module to
bgneal@30: generate 100 values from a Pareto distribution. Plot the CCDF on a log-y scale
bgneal@30: and see if it falls on a straight line. What happens to the curve as you
bgneal@30: increase the number of values?"
bgneal@30: 
bgneal@30: """
bgneal@30: import random
bgneal@30: import sys
bgneal@30: 
bgneal@30: import matplotlib.pyplot as pyplot
bgneal@30: 
bgneal@30: 
bgneal@30: def plot_ccdf_log_log(x_vals, y_vals, title=''):
bgneal@30:     """Given a set of x-values and y-values from a continuous distribution, plot
bgneal@30:     the complementary distribution (CCDF) on a log-log scale.
bgneal@30: 
bgneal@30:     """
bgneal@30:     if len(x_vals) != len(y_vals):
bgneal@30:         raise ValueError
bgneal@30: 
bgneal@30:     ys = [1.0 - y for y in y_vals]
bgneal@30: 
bgneal@30:     pyplot.clf()
bgneal@30:     pyplot.xscale('log')
bgneal@30:     pyplot.yscale('log')
bgneal@30:     pyplot.title(title)
bgneal@30:     pyplot.xlabel('x')
bgneal@30:     pyplot.ylabel('1-y')
bgneal@30:     pyplot.plot(x_vals, ys, label='1-y', color='green', linewidth=3)
bgneal@30:     pyplot.legend(loc='upper right')
bgneal@30:     pyplot.show()
bgneal@30: 
bgneal@30: 
bgneal@30: def main(script, n, alpha):
bgneal@30: 
bgneal@30:     n = int(n)
bgneal@30:     alpha = float(alpha)
bgneal@30: 
bgneal@30:     x_vals = range(n)
bgneal@30:     y_vals = [random.paretovariate(alpha) for x in x_vals]
bgneal@30:     y_vals.sort(reverse=True)
bgneal@30: 
bgneal@30:     plot_ccdf_log_log(x_vals, y_vals, 'paretovariate w/alpha = {}'.format(alpha))
bgneal@30: 
bgneal@30: 
bgneal@30: if __name__ == '__main__':
bgneal@30:     main(*sys.argv)