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annotate ch5ex4.py @ 30:5a9a6d1dbf1b
Chapter 5.4, exercise 4, Pareto distributions.
| author | Brian Neal <bgneal@gmail.com> |
|---|---|
| date | Mon, 07 Jan 2013 20:10:32 -0600 |
| parents | |
| children |
| rev | line source |
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| bgneal@30 | 1 """Chapter 5.3 exercise 4 in Allen Downey's Think Complexity book. |
| bgneal@30 | 2 |
| bgneal@30 | 3 "Write a version of plot_ccdf that plots the complementary CCDF on a log-log |
| bgneal@30 | 4 scale. |
| bgneal@30 | 5 |
| bgneal@30 | 6 To test your function, use paretovariate from the random module to |
| bgneal@30 | 7 generate 100 values from a Pareto distribution. Plot the CCDF on a log-y scale |
| bgneal@30 | 8 and see if it falls on a straight line. What happens to the curve as you |
| bgneal@30 | 9 increase the number of values?" |
| bgneal@30 | 10 |
| bgneal@30 | 11 """ |
| bgneal@30 | 12 import random |
| bgneal@30 | 13 import sys |
| bgneal@30 | 14 |
| bgneal@30 | 15 import matplotlib.pyplot as pyplot |
| bgneal@30 | 16 |
| bgneal@30 | 17 |
| bgneal@30 | 18 def plot_ccdf_log_log(x_vals, y_vals, title=''): |
| bgneal@30 | 19 """Given a set of x-values and y-values from a continuous distribution, plot |
| bgneal@30 | 20 the complementary distribution (CCDF) on a log-log scale. |
| bgneal@30 | 21 |
| bgneal@30 | 22 """ |
| bgneal@30 | 23 if len(x_vals) != len(y_vals): |
| bgneal@30 | 24 raise ValueError |
| bgneal@30 | 25 |
| bgneal@30 | 26 ys = [1.0 - y for y in y_vals] |
| bgneal@30 | 27 |
| bgneal@30 | 28 pyplot.clf() |
| bgneal@30 | 29 pyplot.xscale('log') |
| bgneal@30 | 30 pyplot.yscale('log') |
| bgneal@30 | 31 pyplot.title(title) |
| bgneal@30 | 32 pyplot.xlabel('x') |
| bgneal@30 | 33 pyplot.ylabel('1-y') |
| bgneal@30 | 34 pyplot.plot(x_vals, ys, label='1-y', color='green', linewidth=3) |
| bgneal@30 | 35 pyplot.legend(loc='upper right') |
| bgneal@30 | 36 pyplot.show() |
| bgneal@30 | 37 |
| bgneal@30 | 38 |
| bgneal@30 | 39 def main(script, n, alpha): |
| bgneal@30 | 40 |
| bgneal@30 | 41 n = int(n) |
| bgneal@30 | 42 alpha = float(alpha) |
| bgneal@30 | 43 |
| bgneal@30 | 44 x_vals = range(n) |
| bgneal@30 | 45 y_vals = [random.paretovariate(alpha) for x in x_vals] |
| bgneal@30 | 46 y_vals.sort(reverse=True) |
| bgneal@30 | 47 |
| bgneal@30 | 48 plot_ccdf_log_log(x_vals, y_vals, 'paretovariate w/alpha = {}'.format(alpha)) |
| bgneal@30 | 49 |
| bgneal@30 | 50 |
| bgneal@30 | 51 if __name__ == '__main__': |
| bgneal@30 | 52 main(*sys.argv) |