Lossy-Counting is an approximate frequency counting algorithm proposed by Manku and Motwani in 2002. This module is a Perl implementation of it.
You can count items in data stream which the size is unknown or very large, with small errors and relatively low memory footprint.
#!/usr/bin/env perl
use strict;
use warnings;
use Algorithm::LossyCount;
my @samples = qw/a b a c d f a a d b b c a a .../;
my $counter = Algorithm::LossyCount->new(max_error_ratio => 0.005);
$counter->add_sample($_) for @samples;
my $frequencies = $counter->frequencies;
say $frequencies->{a}; # Approximate freq. of 'a'.
say $frequencies->{b}; # Approximate freq. of 'b'.
...Manku, Gurmeet Singh, and Rajeev Motwani. "Approximate frequency counts over data streams." Proceedings of the 28th international conference on Very Large Data Bases. VLDB Endowment, 2002.
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