think_complexity: ch5ex6-2.py annotate

annotate ch5ex6-2.py @ 39:49db586c727a

Chapter 6, exercise 1: simple program to play with CA and CADrawer.

author	Brian Neal <bgneal@gmail.com>
date	Fri, 11 Jan 2013 21:18:45 -0600
parents	10db8c3a6b83
children

rev	line source
bgneal@35	1 """Chapter 5.5, exercise 6 in Allen Downey's Think Complexity book.
bgneal@35	2
bgneal@35	3 2. Use the WS model to generate the largest graph you can in a reasonable amount
bgneal@35	4 of time. Plot P(k) versus k and see if you can characterize the tail
bgneal@35	5 behavior.
bgneal@35	6
bgneal@35	7 """
bgneal@35	8 import sys
bgneal@35	9
bgneal@35	10 from matplotlib import pyplot
bgneal@35	11
bgneal@35	12 from Graph import Vertex
bgneal@35	13 from SmallWorldGraph import SmallWorldGraph
bgneal@35	14
bgneal@35	15
bgneal@35	16
bgneal@35	17 def main(script, n, k, p):
bgneal@35	18
bgneal@35	19 # create a SmallWorldGraph with n vertices, k regular edges between
bgneal@35	20 # vertices, and rewiring probability p.
bgneal@35	21
bgneal@35	22 n, k, p = int(n), int(k), float(p)
bgneal@35	23 vs = [Vertex() for i in xrange(n)]
bgneal@35	24
bgneal@35	25 g = SmallWorldGraph(vs, k, p)
bgneal@35	26
bgneal@35	27 # retrieve probabilities
bgneal@35	28 p = g.get_p()
bgneal@35	29
bgneal@35	30 # plot P(k) versus k on a log-log scale
bgneal@35	31
bgneal@35	32 vals = p.items()
bgneal@35	33 vals.sort(key=lambda t: t[0])
bgneal@35	34 x, y = zip(*vals)
bgneal@35	35
bgneal@35	36 assert abs(sum(y) - 1.0) < 1e-6
bgneal@35	37
bgneal@35	38 pyplot.clf()
bgneal@35	39 pyplot.xscale('log')
bgneal@35	40 pyplot.yscale('log')
bgneal@35	41 pyplot.title('P(k) versus k')
bgneal@35	42 pyplot.xlabel('k')
bgneal@35	43 pyplot.ylabel('P(k)')
bgneal@35	44 pyplot.plot(x, y, label='P(k) vs. k', color='green', linewidth=3)
bgneal@35	45 pyplot.legend(loc='upper right')
bgneal@35	46 pyplot.show()
bgneal@35	47
bgneal@35	48
bgneal@35	49 if __name__ == '__main__':
bgneal@35	50 main(*sys.argv)

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annotate ch5ex6-2.py @ 39:49db586c727a