NAME
    Algorithm::SlopeOne - Slope One collaborative filtering for rated
    resources

VERSION
    version 0.002

SYNOPSIS
        #!/usr/bin/env perl
        use common::sense;
        use Algorithm::SlopeOne;
        use Data::Printer;

        my $s = Algorithm::SlopeOne->new;
        $s->update([
            {
                squid       => 1.0,
                cuttlefish  => 0.5,
                octopus     => 0.2,
            }, {
                squid       => 1.0,
                octopus     => 0.5,
                nautilus    => 0.2,
            }, {
                squid       => 0.2,
                octopus     => 1.0,
                cuttlefish  => 0.4,
                nautilus    => 0.4,
            }, {
                cuttlefish  => 0.9,
                octopus     => 0.4,
                nautilus    => 0.5,
            },
        ]);
        p $s->predict({ squid => 0.4 });

        # Output:
        # \ {
        #     cuttlefish   0.25,
        #     nautilus     0.1,
        #     octopus      0.233333333333333
        # }

DESCRIPTION
    Perl implementation of the *Weighted Slope One* rating-based
    collaborative filtering scheme.

ATTRIBUTES
  diffs
    Differential ratings matrix.

  freqs
    Ratings count matrix.

METHODS
  clear
    Reset the instance.

  update($userprefs)
    Update matrices with user preference data, accepts a HashRef or an
    ArrayRef of HashRefs:

        $s->predict({ StarWars => 5, LOTR => 5, StarTrek => 3, Prometheus => 1 });
        $s->predict({ StarWars => 3, StarTrek => 5, Prometheus => 4 });
        $s->predict([
            { IronMan => 4, Avengers => 5, XMen => 3 },
            { XMen => 5, DarkKnight => 5, SpiderMan => 3 },
        ]);

  predict($userprefs)
    Recommend new items given known item ratings.

        $s->predict({ StarWars => 5, LOTR => 5, Prometheus => 1 });

REFERENCES
    *   Slope One <https://en.wikipedia.org/wiki/Slope_One> - Wikipedia
        article

    *   Slope One Predictors for Online Rating-Based Collaborative Filtering
        <http://lemire.me/fr/abstracts/SDM2005.html> - original paper

    *   Collaborative filtering made easy
        <http://www.serpentine.com/blog/2006/12/12/collaborative-filtering-m
        ade-easy/> - Python implementation by Bryan O'Sullivan (primary
        reference, test code)

    *   github.com/ashleyw/Slope-One <https://github.com/ashleyw/Slope-One>
        - Ruby port of the above by Ashley Williams (used to borrow test
        code)

    *   Programming Collective Intelligence book
        <http://shop.oreilly.com/product/9780596529321.do> by Toby Segaran

    *   Data Sets by GroupLens Research <http://www.grouplens.org/node/12>

AUTHOR
    Stanislaw Pusep <stas@sysd.org>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2012 by Stanislaw Pusep.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.