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#!/usr/bin/perl
# Produces a graph of random numbers from a Poisson distribution.
use strict;
use warnings;
$| = 1;
use Math::Random::MT::Auto qw(poisson);
MAIN:
{
if (! @ARGV) {
print("Usage: poisson.pl MEAN [COUNT]]\n");
print("\tCOUNT defaults to 1 million\n");
}
my $mean = $ARGV[0];
my $count = (@ARGV > 1) ? $ARGV[1] : 1000000;
my %poisson;
# Get random numbers and put them in bins
print("Generating $count Poisson random numbers. Please wait...");
for (1 .. $count) {
my $x = poisson($mean);
# Make sure the tail doesn't overflow
if ($x > 80) {
$x = 80;
}
$poisson{$x}++;
}
# Find the max bin size for scaling the output
my $max = 0;
while (my $key = each(%poisson)) {
if ($max < $poisson{$key}) {
$max = $poisson{$key};
}
}
# Output the graph
print("\n");
for my $key (sort { $a <=> $b } (keys(%poisson))) {
my $len = int(79.0 * $poisson{$key}/$max);
print(':', '*' x $len, "\n");
}
}
exit(0);
# EOF
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