#!/usr/bin/perl

# Benford's law number generator

# Copyright (C) 2003  Lukasz Debowski <ldebowsk@ipipan.waw.pl>

# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation 
# (http://www.gnu.org/copyleft/gpl.html).

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.


# A short description:

# The program generates real numbers accordingly to the Benford's law.
# The arguments of the program are:

#   benford.pl [how many numbers] 

# We ignore the quality of the standard Perl pseudorandom number generator.



use strict;
use POSIX;

my ($total)=(shift);

if(!defined $total){
    die 
'
Benford\'s law number generator

Copyright (C) 2003  Lukasz Debowski <ldebowsk@ipipan.waw.pl>

The program generates real numbers accordingly to the Benford\'s law.
The arguments of the program are:

  benford.pl [how many numbers] 

';
}

my ($i,$j);
my @count;
my @tab;

for $i (1..$total){
    my $real=exp((rand 1)*log(10));
    $real=~/^(\d)+\.(\d)(\d)/;
    @tab=(0,$1,$2,$3);
    for $j (1..$#tab){
	$count[$j][$tab[$j]]++;
    }
    print "$i: $real\n";
}

for $j (1..$#tab){
    print "Relative frequencies of digits for position no. $j:\n";

    for $i (0..$#{$count[$j]}){
	my $ratio=$count[$j][$i]/$total;
	print "$i: $ratio\n";
    }
}