"""This file contains code for use with "Think Bayes",
by Allen B. Downey, available from greenteapress.com
Copyright 2012 Allen B. Downey
License: GNU GPLv3 http://www.gnu.org/licenses/gpl.html
"""
from __future__ import print_function, division
from dice import Dice
import thinkplot
class Train(Dice):
"""Represents hypotheses about how many trains the company has.
The likelihood function for the train problem is the same as
for the Dice problem.
"""
def Likelihood(self, data, hypo):
N = hypo
k, m = data
if N < m:
return 0
return m ** (k-1) / N**k
def main():
hypos = range(1, 1001)
suite = Train(hypos)
data = 3, 70
suite.Update(data)
print('posterior mean', suite.Mean())
thinkplot.Pmf(suite, label='after 70')
thinkplot.Show(xlabel='Number of trains',
ylabel='PMF')
if __name__ == '__main__':
main()
