AI-NaiveBayes

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Changes  view on Meta::CPAN

Revision history for AI::NaiveBayes

0.04      2017-01-20
   Some doc fixes
   Moved do my personal github repo

0.03
   Synopsis example fixed

0.02
   added 'train' class method for quick start

0.01
   initial release 

INSTALL  view on Meta::CPAN

This is the Perl distribution AI-NaiveBayes.

Installing AI-NaiveBayes is straightforward.

## Installation with cpanm

If you have cpanm, you only need one line:

    % cpanm AI::NaiveBayes

If it does not have permission to install modules to the current perl, cpanm
will automatically set up and install to a local::lib in your home directory.
See the local::lib documentation (https://metacpan.org/pod/local::lib) for
details on enabling it in your environment.

## Installing with the CPAN shell

Alternatively, if your CPAN shell is set up, you should just be able to do:

    % cpan AI::NaiveBayes

## Manual installation

As a last resort, you can manually install it. Download the tarball, untar it,
then build it:

    % perl Makefile.PL
    % make && make test

Then install it:

    % make install

If your perl is system-managed, you can create a local::lib in your home
directory to install modules to. For details, see the local::lib documentation:
https://metacpan.org/pod/local::lib

## Documentation

AI-NaiveBayes documentation is available as POD.
You can run perldoc from a shell to read the documentation:

    % perldoc AI::NaiveBayes

LICENSE  view on Meta::CPAN

This software is copyright (c) 2012 by Opera Software ASA.

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

Terms of the Perl programming language system itself

a) the GNU General Public License as published by the Free
   Software Foundation; either version 1, or (at your option) any
   later version, or
b) the "Artistic License"

--- The GNU General Public License, Version 1, February 1989 ---

This software is Copyright (c) 2012 by Opera Software ASA.

This is free software, licensed under:

  The GNU General Public License, Version 1, February 1989

                    GNU GENERAL PUBLIC LICENSE
                     Version 1, February 1989

 Copyright (C) 1989 Free Software Foundation, Inc.
 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

                            Preamble

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That's all there is to it!


--- The Artistic License 1.0 ---

This software is Copyright (c) 2012 by Opera Software ASA.

This is free software, licensed under:

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MANIFEST  view on Meta::CPAN

# This file was automatically generated by Dist::Zilla::Plugin::Manifest v6.008.
Changes
INSTALL
LICENSE
MANIFEST
META.json
META.yml
Makefile.PL
README
README.pod
a
dist.ini
lib/AI/NaiveBayes.pm
lib/AI/NaiveBayes/Classification.pm
lib/AI/NaiveBayes/Learner.pm
t/01-learner.t
t/02-predict.t
t/author-pod-coverage.t
t/author-pod-syntax.t
t/default_training.t

META.json  view on Meta::CPAN

{
   "abstract" : "A Bayesian classifier",
   "author" : [
      "Zbigniew Lukasiak <zlukasiak@opera.com>",
      "Tadeusz So\u015bnierz <tsosnierz@opera.com>",
      "Ken Williams <ken@mathforum.org>"
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      "version" : 2
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   "name" : "AI-NaiveBayes",
   "no_index" : {
      "directory" : [
         "examples",
         "t/lib"
      ]
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   "prereqs" : {
      "configure" : {
         "requires" : {
            "ExtUtils::MakeMaker" : "0"
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            "Test::Pod" : "1.41",
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            "strict" : "0",
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         "requires" : {
            "Test::More" : "0"
         }
      }
   },
   "release_status" : "stable",
   "resources" : {
      "repository" : {
         "type" : "git",
         "web" : "http://github.com/zby/AI-NaiveBayes"
      }
   },
   "version" : "0.04",
   "x_contributors" : [
      "schweickism <schweickism@hotmail.com>",
      "Zbigniew \u0141ukasiak <zzbbyy@gmail.com>"
   ],
   "x_serialization_backend" : "Cpanel::JSON::XS version 3.0225"
}

META.yml  view on Meta::CPAN

---
abstract: 'A Bayesian classifier'
author:
  - 'Zbigniew Lukasiak <zlukasiak@opera.com>'
  - 'Tadeusz Sośnierz <tsosnierz@opera.com>'
  - 'Ken Williams <ken@mathforum.org>'
build_requires:
  Test::More: '0'
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  ExtUtils::MakeMaker: '0'
dynamic_config: 0
generated_by: 'Dist::Zilla version 6.008, CPAN::Meta::Converter version 2.150005'
license: perl
meta-spec:
  url: http://module-build.sourceforge.net/META-spec-v1.4.html
  version: '1.4'
name: AI-NaiveBayes
no_index:
  directory:
    - examples
    - t/lib
requires:
  File::Find::Rule: '0.32'
  List::Util: '0'
  Moose: '1.15'
  MooseX::Storage: '0.25'
  perl: '5.010'
  strict: '0'
  warnings: '0'
resources:
  repository: http://github.com/zby/AI-NaiveBayes
version: '0.04'
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  - 'Zbigniew Łukasiak <zzbbyy@gmail.com>'
x_serialization_backend: 'YAML::Tiny version 1.69'

Makefile.PL  view on Meta::CPAN

# This file was automatically generated by Dist::Zilla::Plugin::MakeMaker v6.008.
use strict;
use warnings;

use 5.010;

use ExtUtils::MakeMaker;

my %WriteMakefileArgs = (
  "ABSTRACT" => "A Bayesian classifier",
  "AUTHOR" => "Zbigniew Lukasiak <zlukasiak\@opera.com>, Tadeusz So\x{15b}nierz <tsosnierz\@opera.com>, Ken Williams <ken\@mathforum.org>",
  "CONFIGURE_REQUIRES" => {
    "ExtUtils::MakeMaker" => 0
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  "DISTNAME" => "AI-NaiveBayes",
  "LICENSE" => "perl",
  "MIN_PERL_VERSION" => "5.010",
  "NAME" => "AI::NaiveBayes",
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    "File::Find::Rule" => "0.32",
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    "Test::More" => 0
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  "VERSION" => "0.04",
  "test" => {
    "TESTS" => "t/*.t"
  }
);


my %FallbackPrereqs = (
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  "Moose" => "1.15",
  "MooseX::Storage" => "0.25",
  "Test::More" => 0,
  "strict" => 0,
  "warnings" => 0
);


unless ( eval { ExtUtils::MakeMaker->VERSION(6.63_03) } ) {
  delete $WriteMakefileArgs{TEST_REQUIRES};
  delete $WriteMakefileArgs{BUILD_REQUIRES};
  $WriteMakefileArgs{PREREQ_PM} = \%FallbackPrereqs;
}

delete $WriteMakefileArgs{CONFIGURE_REQUIRES}
  unless eval { ExtUtils::MakeMaker->VERSION(6.52) };

WriteMakefile(%WriteMakefileArgs);

README  view on Meta::CPAN



This archive contains the distribution AI-NaiveBayes,
version 0.04:

  A Bayesian classifier

This software is copyright (c) 2012 by Opera Software ASA.

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


This README file was generated by Dist::Zilla::Plugin::Readme v6.008.

README.pod  view on Meta::CPAN

package AI::NaiveBayes;

use strict;
use warnings;
use 5.010;
use AI::NaiveBayes::Classification;
use AI::NaiveBayes::Learner;
use Moose;
use MooseX::Storage;

use List::Util qw(max);

with Storage(format => 'Storable', io => 'File');

has model   => (is => 'ro', isa => 'HashRef[HashRef]', required => 1);

sub train {
    my $self = shift;
    my $learner = AI::NaiveBayes::Learner->new();
    for my $example ( @_ ){
        $learner->add_example( %$example );
    }
    return $learner->classifier;
}


sub classify {
    my ($self, $newattrs) = @_;
    $newattrs or die "Missing parameter for classify()";

    my $m = $self->model;

    # Note that we're using the log(prob) here.  That's why we add instead of multiply.

    my %scores = %{$m->{prior_probs}};
    my %features;
    while (my ($feature, $value) = each %$newattrs) {
        next unless exists $m->{attributes}{$feature};  # Ignore totally unseen features
        while (my ($label, $attributes) = each %{$m->{probs}}) {
            my $score = ($attributes->{$feature} || $m->{smoother}{$label})*$value;  # P($feature|$label)**$value
            $scores{$label} += $score;
            $features{$feature}{$label} = $score;
        }
    }

    rescale(\%scores);

    return AI::NaiveBayes::Classification->new( label_sums => \%scores, features => \%features );
}

sub rescale {
    my ($scores) = @_;

    # Scale everything back to a reasonable area in logspace (near zero), un-loggify, and normalize
    my $total = 0;
    my $max = max(values %$scores);
    foreach (values %$scores) {
        $_ = exp($_ - $max);
        $total += $_**2;
    }
    $total = sqrt($total);
    foreach (values %$scores) {
        $_ /= $total;
    }
}


__PACKAGE__->meta->make_immutable;

1;
__END__


# ABSTRACT: A Bayesian classifier

=encoding utf8

=head1 SYNOPSIS

    # AI::NaiveBayes objects are created by AI::NaiveBayes::Learner
    # but for quick start you can use the 'train' class method
    # that is a shortcut using default AI::NaiveBayes::Learner settings

    my $classifier = AI::NaiveBayes->train( 
        {
            attributes => {
                sheep => 1, very => 1,  valuable => 1, farming => 1
            },
            labels => ['farming']
        },
        {
            attributes => {
                vampires => 1, cannot => 1, see => 1, their => 1,
                images => 1, mirrors => 1
            },
            labels => ['vampire']
        },
    );

    # Classify a feature vector
    my $result = $classifier->classify({bar => 3, blurp => 2});
    
    # $result is now a AI::NaiveBayes::Classification object
    
    my $best_category = $result->best_category;
    
=head1 DESCRIPTION

This module implements the classic "Naive Bayes" machine learning
algorithm.  This is a low level class that accepts only pre-computed feature-vectors
as input, see L<AI::Classifier::Text> for a text classifier that uses
this class.  

Creation of C<AI::NaiveBayes> classifier object out of training
data is done by L<AI::NaiveBayes::Learner>. For quick start 
you can use the limited C<train> class method that trains the 
classifier in a default way.

The classifier object is immutable.

It is a well-studied probabilistic algorithm often used in
automatic text categorization.  Compared to other algorithms (kNN,
SVM, Decision Trees), it's pretty fast and reasonably competitive in
the quality of its results.

A paper by Fabrizio Sebastiani provides a really good introduction to
text categorization:
L<http://faure.iei.pi.cnr.it/~fabrizio/Publications/ACMCS02.pdf>

=head1 METHODS

=over 4

=item new( model => $model )

Internal. See L<AI::NaiveBayes::Learner> to learn how to create a C<AI::NaiveBayes>
classifier from training data.

=item train( LIST of HASHREFS )

Shortcut for creating a trained classifier using L<AI::NaiveBayes::Learner> default
settings. 
Arguments are passed to the C<add_example> method of the L<AI::NaiveBayes::Learner>
object one by one.

=item classify( HASHREF )

Classifies a feature-vector of the form:

    { feature1 => weight1, feature2 => weight2, ... }
    
The result is a C<AI::NaiveBayes::Classification> object.

=item rescale

Internal

=back

=head1 ATTRIBUTES 

=over 4

=item model

Internal

=back

=head1 THEORY

Bayes' Theorem is a way of inverting a conditional probability. It
states:

    P(y|x) P(x)
        P(x|y) = -------------
    P(y)

The notation C<P(x|y)> means "the probability of C<x> given C<y>."  See also
L<"http://mathforum.org/dr.math/problems/battisfore.03.22.99.html">
for a simple but complete example of Bayes' Theorem.

In this case, we want to know the probability of a given category given a
certain string of words in a document, so we have:

    P(words | cat) P(cat)
        P(cat | words) = --------------------
    P(words)

We have applied Bayes' Theorem because C<P(cat | words)> is a difficult
quantity to compute directly, but C<P(words | cat)> and C<P(cat)> are accessible
(see below).

The greater the expression above, the greater the probability that the given
document belongs to the given category.  So we want to find the maximum
value.  We write this as

    P(words | cat) P(cat)
        Best category =   ArgMax      -----------------------
    cat in cats          P(words)


Since C<P(words)> doesn't change over the range of categories, we can get rid
of it.  That's good, because we didn't want to have to compute these values
anyway.  So our new formula is:

    Best category =   ArgMax      P(words | cat) P(cat)
        cat in cats

Finally, we note that if C<w1, w2, ... wn> are the words in the document,
then this expression is equivalent to:

    Best category =   ArgMax      P(w1|cat)*P(w2|cat)*...*P(wn|cat)*P(cat)
        cat in cats

That's the formula I use in my document categorization code.  The last
step is the only non-rigorous one in the derivation, and this is the
"naive" part of the Naive Bayes technique.  It assumes that the
probability of each word appearing in a document is unaffected by the
presence or absence of each other word in the document.  We assume
this even though we know this isn't true: for example, the word
"iodized" is far more likely to appear in a document that contains the
word "salt" than it is to appear in a document that contains the word
"subroutine".  Luckily, as it turns out, making this assumption even
when it isn't true may have little effect on our results, as the
following paper by Pedro Domingos argues:
L<"http://www.cs.washington.edu/homes/pedrod/mlj97.ps.gz">

=head1 SEE ALSO

Algorithm::NaiveBayes (3), AI::Classifier::Text(3) 

=head1 BASED ON

Much of the code and description is from L<Algorithm::NaiveBayes>.

=cut

a  view on Meta::CPAN

name    = AI-NaiveBayes
author  = Zbigniew Lukasiak <zlukasiak@opera.com>
author  = Tadeusz Sośnierz <tsosnierz@opera.com>
author  = Ken Williams <ken@mathforum.org>
[Git::Contributors]
license = Perl_5
copyright_holder = Opera Software ASA
copyright_year   = 2012
version = 0.04
[@Basic]
[AutoPrereqs]
[Prereqs]
Moose = 1.15
MooseX::Storage = 0.25
File::Find::Rule = 0.32
[TestRelease]
[PkgVersion]
[MetaNoIndex]
directory = t/lib
directory = examples
[InstallGuide]
[MetaJSON]
[MetaResources]
repository.web   = http://github.com/zby/AI-NaiveBayes
repository.type  = git

[NextRelease]
format = %-9v %{yyyy-MM-dd}d
[CheckChangeLog]
[PodSyntaxTests]
[PodCoverageTests]
[PodWeaver]

dist.ini  view on Meta::CPAN

name    = AI-NaiveBayes
author  = Zbigniew Lukasiak <zlukasiak@opera.com>
author  = Tadeusz Sośnierz <tsosnierz@opera.com>
author  = Ken Williams <ken@mathforum.org>
license = Perl_5
copyright_holder = Opera Software ASA
copyright_year   = 2012
version = 0.04
[@Basic]
[AutoPrereqs]
[Prereqs]
Moose = 1.15
MooseX::Storage = 0.25
File::Find::Rule = 0.32
[TestRelease]
[PkgVersion]
[MetaNoIndex]
directory = t/lib
directory = examples
[InstallGuide]
[MetaJSON]
[MetaResources]
repository.web   = http://github.com/zby/AI-NaiveBayes
repository.type  = git

[NextRelease]
format = %-9v %{yyyy-MM-dd}d
[CheckChangeLog]
[PodSyntaxTests]
[PodCoverageTests]
[PodWeaver]
[Git::Contributors]

lib/AI/NaiveBayes.pm  view on Meta::CPAN

package AI::NaiveBayes;
$AI::NaiveBayes::VERSION = '0.04';
use strict;
use warnings;
use 5.010;
use AI::NaiveBayes::Classification;
use AI::NaiveBayes::Learner;
use Moose;
use MooseX::Storage;

use List::Util qw(max);

with Storage(format => 'Storable', io => 'File');

has model   => (is => 'ro', isa => 'HashRef[HashRef]', required => 1);

sub train {
    my $self = shift;
    my $learner = AI::NaiveBayes::Learner->new();
    for my $example ( @_ ){
        $learner->add_example( %$example );
    }
    return $learner->classifier;
}


sub classify {
    my ($self, $newattrs) = @_;
    $newattrs or die "Missing parameter for classify()";

    my $m = $self->model;

    # Note that we're using the log(prob) here.  That's why we add instead of multiply.

    my %scores = %{$m->{prior_probs}};
    my %features;
    while (my ($feature, $value) = each %$newattrs) {
        next unless exists $m->{attributes}{$feature};  # Ignore totally unseen features
        while (my ($label, $attributes) = each %{$m->{probs}}) {
            my $score = ($attributes->{$feature} || $m->{smoother}{$label})*$value;  # P($feature|$label)**$value
            $scores{$label} += $score;
            $features{$feature}{$label} = $score;
        }
    }

    rescale(\%scores);

    return AI::NaiveBayes::Classification->new( label_sums => \%scores, features => \%features );
}

sub rescale {
    my ($scores) = @_;

    # Scale everything back to a reasonable area in logspace (near zero), un-loggify, and normalize
    my $total = 0;
    my $max = max(values %$scores);
    foreach (values %$scores) {
        $_ = exp($_ - $max);
        $total += $_**2;
    }
    $total = sqrt($total);
    foreach (values %$scores) {
        $_ /= $total;
    }
}


__PACKAGE__->meta->make_immutable;

1;

=pod

=encoding UTF-8

=head1 NAME

AI::NaiveBayes - A Bayesian classifier

=head1 VERSION

version 0.04

=head1 SYNOPSIS

    # AI::NaiveBayes objects are created by AI::NaiveBayes::Learner
    # but for quick start you can use the 'train' class method
    # that is a shortcut using default AI::NaiveBayes::Learner settings

    my $classifier = AI::NaiveBayes->train( 
        {
            attributes => {
                sheep => 1, very => 1,  valuable => 1, farming => 1
            },
            labels => ['farming']
        },
        {
            attributes => {
                vampires => 1, cannot => 1, see => 1, their => 1,
                images => 1, mirrors => 1
            },
            labels => ['vampire']
        },
    );

    # Classify a feature vector
    my $result = $classifier->classify({bar => 3, blurp => 2});
    
    # $result is now a AI::NaiveBayes::Classification object
    
    my $best_category = $result->best_category;

=head1 DESCRIPTION

This module implements the classic "Naive Bayes" machine learning
algorithm.  This is a low level class that accepts only pre-computed feature-vectors
as input, see L<AI::Classifier::Text> for a text classifier that uses
this class.  

Creation of C<AI::NaiveBayes> classifier object out of training
data is done by L<AI::NaiveBayes::Learner>. For quick start 
you can use the limited C<train> class method that trains the 
classifier in a default way.

The classifier object is immutable.

It is a well-studied probabilistic algorithm often used in
automatic text categorization.  Compared to other algorithms (kNN,
SVM, Decision Trees), it's pretty fast and reasonably competitive in
the quality of its results.

A paper by Fabrizio Sebastiani provides a really good introduction to
text categorization:
L<http://faure.iei.pi.cnr.it/~fabrizio/Publications/ACMCS02.pdf>

=head1 METHODS

=over 4

=item new( model => $model )

Internal. See L<AI::NaiveBayes::Learner> to learn how to create a C<AI::NaiveBayes>
classifier from training data.

=item train( LIST of HASHREFS )

Shortcut for creating a trained classifier using L<AI::NaiveBayes::Learner> default
settings. 
Arguments are passed to the C<add_example> method of the L<AI::NaiveBayes::Learner>
object one by one.

=item classify( HASHREF )

Classifies a feature-vector of the form:

    { feature1 => weight1, feature2 => weight2, ... }

The result is a C<AI::NaiveBayes::Classification> object.

=item rescale

Internal

=back

=head1 ATTRIBUTES 

=over 4

=item model

Internal

=back

=head1 THEORY

Bayes' Theorem is a way of inverting a conditional probability. It
states:

    P(y|x) P(x)
        P(x|y) = -------------
    P(y)

The notation C<P(x|y)> means "the probability of C<x> given C<y>."  See also
L<"http://mathforum.org/dr.math/problems/battisfore.03.22.99.html">
for a simple but complete example of Bayes' Theorem.

In this case, we want to know the probability of a given category given a
certain string of words in a document, so we have:

    P(words | cat) P(cat)
        P(cat | words) = --------------------
    P(words)

We have applied Bayes' Theorem because C<P(cat | words)> is a difficult
quantity to compute directly, but C<P(words | cat)> and C<P(cat)> are accessible
(see below).

The greater the expression above, the greater the probability that the given
document belongs to the given category.  So we want to find the maximum
value.  We write this as

    P(words | cat) P(cat)
        Best category =   ArgMax      -----------------------
    cat in cats          P(words)

Since C<P(words)> doesn't change over the range of categories, we can get rid
of it.  That's good, because we didn't want to have to compute these values
anyway.  So our new formula is:

    Best category =   ArgMax      P(words | cat) P(cat)
        cat in cats

Finally, we note that if C<w1, w2, ... wn> are the words in the document,
then this expression is equivalent to:

    Best category =   ArgMax      P(w1|cat)*P(w2|cat)*...*P(wn|cat)*P(cat)
        cat in cats

That's the formula I use in my document categorization code.  The last
step is the only non-rigorous one in the derivation, and this is the
"naive" part of the Naive Bayes technique.  It assumes that the
probability of each word appearing in a document is unaffected by the
presence or absence of each other word in the document.  We assume
this even though we know this isn't true: for example, the word
"iodized" is far more likely to appear in a document that contains the
word "salt" than it is to appear in a document that contains the word
"subroutine".  Luckily, as it turns out, making this assumption even
when it isn't true may have little effect on our results, as the
following paper by Pedro Domingos argues:
L<"http://www.cs.washington.edu/homes/pedrod/mlj97.ps.gz">

=head1 SEE ALSO

Algorithm::NaiveBayes (3), AI::Classifier::Text(3) 

=head1 BASED ON

Much of the code and description is from L<Algorithm::NaiveBayes>.

=head1 AUTHORS

=over 4

=item *

Zbigniew Lukasiak <zlukasiak@opera.com>

=item *

Tadeusz Sośnierz <tsosnierz@opera.com>

=item *

Ken Williams <ken@mathforum.org>

=back

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2012 by Opera Software ASA.

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

=cut

__END__


# ABSTRACT: A Bayesian classifier

lib/AI/NaiveBayes/Classification.pm  view on Meta::CPAN

package AI::NaiveBayes::Classification;
$AI::NaiveBayes::Classification::VERSION = '0.04';
use strict;
use warnings;
use 5.010;
use Moose;

has features => (is => 'ro', isa => 'HashRef[HashRef]', required => 1);
has label_sums => (is => 'ro', isa => 'HashRef', required => 1);
has best_category => (is => 'ro', isa => 'Str', lazy_build => 1);

sub _build_best_category {
    my $self = shift;
    my $sc = $self->label_sums;

    my ($best_cat, $best_score) = each %$sc;
    while (my ($key, $val) = each %$sc) {
        ($best_cat, $best_score) = ($key, $val) if $val > $best_score;
    }
    return $best_cat;
}

sub find_predictors{
    my $self = shift;

    my $best_cat = $self->best_category;
    my $features = $self->features;
    my @predictors; 
    for my $feature ( keys %$features  ) {
        for my $cat ( keys %{ $features->{$feature } } ){
            next if $cat eq $best_cat;
            push @predictors, [ $feature, $features->{$feature}{$best_cat} - $features->{$feature}{$cat} ];
        }
    }
    @predictors = sort { abs( $b->[1] ) <=> abs( $a->[1] ) } @predictors;
    return $best_cat, @predictors;
}


__PACKAGE__->meta->make_immutable;

1;

=pod

=encoding UTF-8

=head1 NAME

AI::NaiveBayes::Classification - The result of a bayesian classification

=head1 VERSION

version 0.04

=head1 SYNOPSIS

    my $result = $classifier->classify({bar => 3, blurp => 2});
    # $result is an AI::NaiveBayes::Classification object
    say $result->best_category;
    my $predictors = $result->find_predictors;

=head1 DESCRIPTION

AI::NaiveBayes::Classification represents the result of a bayesian classification,
produced by AI::NaiveBayes classifier.

=head1 METHODS

=over 4

=item C<best_category()>

Returns a string being a label that suits given document the best.

=item C<find_predictors()>

This method returns the C<best_category()>, as well as the list of all the predictors
along with their influence on the best category selected. So the second value
returned is a list of array references, where each one contains a string being a
single feature and a number describing its influence on the result. So the
second part of the result may look like this:

    (
        [ 'activities',  1.2511540632952 ],
        [ 'over',       -1.0269523272981 ],
        [ 'provide',     0.8280157033269 ],
        [ 'natural',     0.7361042359385 ],
        [ 'against',    -0.6923354975173 ],
    )

=back

=head1 SEE ALSO

AI::NaiveBayes (3), AI::Classifier(3)

=head1 AUTHORS

=over 4

=item *

Zbigniew Lukasiak <zlukasiak@opera.com>

=item *

Tadeusz Sośnierz <tsosnierz@opera.com>

=item *

Ken Williams <ken@mathforum.org>

=back

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2012 by Opera Software ASA.

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

=cut

__END__

# ABSTRACT: The result of a bayesian classification

lib/AI/NaiveBayes/Learner.pm  view on Meta::CPAN

package AI::NaiveBayes::Learner;
$AI::NaiveBayes::Learner::VERSION = '0.04';
use strict;
use warnings;
use 5.010;

use List::Util qw( min sum );
use Moose;
use AI::NaiveBayes;

has attributes => (is => 'ro', isa => 'HashRef', default => sub { {} }, clearer => '_clear_attrs');
has labels     => (is => 'ro', isa => 'HashRef', default => sub { {} }, clearer => '_clear_labels');
has examples  => (is => 'ro', isa => 'Int',     default => 0, clearer => '_clear_examples');

has features_kept => (is => 'ro', predicate => 'limit_features');

has classifier_class => ( is => 'ro', isa => 'Str', default => 'AI::NaiveBayes' );

sub add_example {
    my ($self, %params) = @_;
    for ('attributes', 'labels') {
        die "Missing required '$_' parameter" unless exists $params{$_};
    }

    $self->{examples}++;

    my $attributes = $params{attributes};
    my $labels     = $params{labels};

    add_hash($self->attributes(), $attributes);

    my $our_labels = $self->labels;
    foreach my $label ( @$labels ) {
        $our_labels->{$label}{count}++;
        $our_labels->{$label}{attributes} //= {};
        add_hash($our_labels->{$label}{attributes}, $attributes);
    }
}

sub classifier {
    my $self = shift;

    my $examples    = $self->examples;
    my $labels       = $self->labels;
    my $vocab_size   = keys %{ $self->attributes };
    my $model;
    $model->{attributes} = $self->attributes;


    # Calculate the log-probabilities for each category
    foreach my $label (keys %$labels) {
        $model->{prior_probs}{$label} = log($labels->{$label}{count} / $examples);

        # Count the number of tokens in this cat
        my $label_tokens = sum( values %{ $labels->{$label}{attributes} } );

        # Compute a smoothing term so P(word|cat)==0 can be avoided
        $model->{smoother}{$label} = -log($label_tokens + $vocab_size);

        # P(attr|label) = $count/$label_tokens                         (simple)
        # P(attr|label) = ($count + 1)/($label_tokens + $vocab_size)   (with smoothing)
        # log P(attr|label) = log($count + 1) - log($label_tokens + $vocab_size)

        my $denominator = log($label_tokens + $vocab_size);

        while (my ($attribute, $count) = each %{ $labels->{$label}{attributes} }) {
            $model->{probs}{$label}{$attribute} = log($count + 1) - $denominator;
        }

        if ($self->limit_features) {
            my %old  = %{$model->{probs}{$label}};
            my @features = sort { abs($old{$a}) <=> abs($old{$b}) } keys(%old);
            my $limit = min($self->features_kept, 0+@features);
            if ($limit < 1) {
                $limit = int($limit * keys(%old));
            }
            my @top = @features[0..$limit-1];
            my %kept = map { $_ => $old{$_} } @top;
            $model->{probs}{$label} = \%kept;
        }
    }
    my $classifier_class = $self->classifier_class;
    return $classifier_class->new( model => $model );
}

sub add_hash {
    my ($first, $second) = @_;
    $first //= {};
    foreach my $k (keys %$second) {
        $first->{$k} //= 0;
        $first->{$k} += $second->{$k};
    }
}

__PACKAGE__->meta->make_immutable;

1;

=pod

=encoding UTF-8

=head1 NAME

AI::NaiveBayes::Learner - Build AI::NaiveBayes classifier from a set of training examples.

=head1 VERSION

version 0.04

=head1 SYNOPSIS

    my $learner = AI::NaiveBayes::Learner->new(features_kept => 0.5);
    $learner->add_example(
        attributes => { sheep => 1, very => 1, valuable => 1, farming => 1 },
        labels => ['farming'] 
    );

    my $classifier = $learner->classifier;

=head1 DESCRIPTION

This is a trainer of AI::NaiveBayes classifiers.  It saves information passed
by the C<add_example> method from
training data into internal structures and then constructs a classifier when
the C<classifier> method is called.

=head1 ATTRIBUTES

=over 4

=item C<features_kept>

Indicates how many features should remain after calculating probabilities. By
default all of them will be kept. For C<features_kept> > 1, C<features_kept> of
features will be preserved. For values lower than 1, a specified fraction of 
features will be kept (e.g. top 20% of features for C<features_kept> = 0.2).

The rest of the attributes is for class' internal usage, and thus not
documented.

=item C<classifier_class>

The class of the classifier to be created.  By default it is
C<AI::NaiveBayes>

=back

=head1 METHODS

=over 4

=item C<add_example( attributes => HASHREF, labels => LIST )>

Saves the information from a training example into internal data structures.
C<attributes> should be of the form of 
    { feature1 => weight1, feature2 => weight2, ... }
C<labels> should be a list of strings denoting one or more classes to which the example belongs.

=item C<classifier()>

    Creates an AI::NaiveBayes classifier based on the data accumulated before.

=back

=head1 UTILITY SUBS

=over 4

=item C<add_hash>

=back

=head1 BASED ON

Much of the code and description is from L<Algorithm::NaiveBayes>.

=head1 AUTHORS

=over 4

=item *

Zbigniew Lukasiak <zlukasiak@opera.com>

=item *

Tadeusz Sośnierz <tsosnierz@opera.com>

=item *

Ken Williams <ken@mathforum.org>

=back

=head1 COPYRIGHT AND LICENSE

This software is copyright (c) 2012 by Opera Software ASA.

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

=cut

__END__

# ABSTRACT: Build AI::NaiveBayes classifier from a set of training examples.

t/01-learner.t  view on Meta::CPAN

use strict;
use warnings;
use Test::More tests => 11;
use AI::NaiveBayes::Learner;
ok(1); # If we made it this far, we're loaded.

my $learner = AI::NaiveBayes::Learner->new();

# Populate
$learner->add_example( attributes => _hash(qw(sheep very valuable farming)),
		   labels => ['farming'] );
is $learner->{labels}{farming}{count}, 1;

$learner->add_example( attributes => _hash(qw(farming requires many kinds animals)),
		   labels => ['farming'] );
is $learner->{labels}{farming}{count}, 2;
is keys %{$learner->{labels}}, 1;

$learner->add_example( attributes => _hash(qw(vampires drink blood vampires may staked)),
		   labels => ['vampire'] );
is $learner->{labels}{vampire}{count}, 1;

$learner->add_example( attributes => _hash(qw(vampires cannot see their images mirrors)),
		   labels => ['vampire'] );
is $learner->{labels}{vampire}{count}, 2;
is keys %{$learner->{labels}}, 2;

# features_kept > 1
$learner = AI::NaiveBayes::Learner->new(features_kept => 5);
$learner->add_example( attributes => _hash(qw(one two three four)),
		   labels => ['farming'] );
$learner->add_example( attributes => _hash(qw(five six seven eight)),
		   labels => ['farming'] );
$learner->add_example( attributes => _hash(qw(one two three four five)),
		   labels => ['farming'] );
my $model = $learner->classifier->model;
is keys %{$model->{probs}{farming}}, 5, '5 features kept';
is join(" ", sort { $a cmp $b } keys %{$model->{probs}{farming}}), 'five four one three two';

# features_kept < 1
$learner = AI::NaiveBayes::Learner->new(features_kept => 0.5);
$learner->add_example( attributes => _hash(qw(one two three four)),
		   labels => ['farming'] );
$learner->add_example( attributes => _hash(qw(five six seven eight)),
		   labels => ['farming'] );
$learner->add_example( attributes => _hash(qw(one two three four)),
		   labels => ['farming'] );
$model = $learner->classifier->model;
is keys %{$model->{probs}{farming}}, 4, 'half features kept';
is join(" ", sort { $a cmp $b } keys %{$model->{probs}{farming}}), 'four one three two';

sub _hash { +{ map {$_,1} @_ } }

t/02-predict.t  view on Meta::CPAN

use strict;
use warnings;
use Test::More tests => 12;
use AI::NaiveBayes;
use AI::NaiveBayes::Learner;
ok(1); # If we made it this far, we're loaded.

my $lr = AI::NaiveBayes::Learner->new();

# Populate
$lr->add_example( attributes => _hash(qw(sheep very valuable farming)),
           labels => ['farming'] );
$lr->add_example( attributes => _hash(qw(farming requires many kinds animals)),
           labels => ['farming'] );
$lr->add_example( attributes => _hash(qw(vampires drink blood vampires may staked)),
           labels => ['vampire'] );
$lr->add_example( attributes => _hash(qw(vampires cannot see their images mirrors)),
           labels => ['vampire'] );

my $classifier = $lr->classifier;
ok $classifier;

# Predict
my $s = $classifier->classify( _hash(qw(i would like to begin farming sheep)) );
my $h = $s->label_sums;
ok $h;
ok $h->{farming} > 0.5;
ok $h->{vampire} < 0.5;

$s = $classifier->classify( _hash(qw(i see that many vampires may have eaten my beautiful daughter's blood)) );
$h = $s->label_sums;
ok $h;
ok $h->{farming} < 0.5;
ok $h->{vampire} > 0.5;

# Find predictors

my $p = $classifier->classify( _hash( qw(i would like to begin farming sheep)) );
my( $best_cat, @predictors ) = $p->find_predictors();
is( $best_cat, 'farming', 'Best category' );
is( scalar @predictors, 2, 'farming and sheep - two predictors' );
is( $predictors[0][0], 'farming', 'Farming is the best predictor' );

# Prior probs
$lr = AI::NaiveBayes::Learner->new();

# Populate
$lr->add_example( attributes => _hash(qw(sheep very valuable farming)),
           labels => ['farming'] );
$lr->add_example( attributes => _hash(qw(farming requires many kinds animals)),
           labels => ['farming'] );
$lr->add_example( attributes => _hash(qw(good soil)),
           labels => ['farming'] );
$lr->add_example( attributes => _hash(qw(vampires drink blood vampires may staked)),
           labels => ['vampire'] );

$classifier = $lr->classifier;

# Predict
$s = $classifier->classify( _hash(qw(jakis tekst po polsku)) );
$h = $s->label_sums;
ok(abs( 3 - $h->{farming} / $h->{vampire} ) < 0.01, 'Prior probabillities' );


################################################################
sub _hash { +{ map {$_,1} @_ } }

t/author-pod-coverage.t  view on Meta::CPAN

#!perl

BEGIN {
  unless ($ENV{AUTHOR_TESTING}) {
    print qq{1..0 # SKIP these tests are for testing by the author\n};
    exit
  }
}

# This file was automatically generated by Dist::Zilla::Plugin::PodCoverageTests.

use Test::Pod::Coverage 1.08;
use Pod::Coverage::TrustPod;

all_pod_coverage_ok({ coverage_class => 'Pod::Coverage::TrustPod' });

t/author-pod-syntax.t  view on Meta::CPAN

#!perl

BEGIN {
  unless ($ENV{AUTHOR_TESTING}) {
    print qq{1..0 # SKIP these tests are for testing by the author\n};
    exit
  }
}

# This file was automatically generated by Dist::Zilla::Plugin::PodSyntaxTests.
use strict; use warnings;
use Test::More;
use Test::Pod 1.41;

all_pod_files_ok();

t/default_training.t  view on Meta::CPAN

use strict;
use Test::More tests => 2;
use AI::NaiveBayes;
ok(1); # If we made it this far, we're loaded.

my $classifier = AI::NaiveBayes->train( 
    {
        attributes => _hash(qw(sheep very valuable farming)),
        labels => ['farming']
    },
    {
        attributes => _hash(qw(vampires cannot see their images mirrors)),
        labels => ['vampire']
    },
);

isa_ok( $classifier, 'AI::NaiveBayes' );


################################################################
sub _hash { +{ map {$_,1} @_ } }

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