File Coverage

blib/lib/Lingua/JA/OkapiBM25.pm

Criterion	Covered	Total	%
statement	7	9	77.7
branch			n/a
condition			n/a
subroutine	3	3	100.0
pod			n/a
total	10	12	83.3

package Lingua::JA::OkapiBM25;

use strict;
use warnings;
use Lingua::JA::OkapiBM25::Result;
use base qw( Lingua::JA::TFIDF);
use 5.008_001;

our $VERSION = '0.00001';

__PACKAGE__->mk_accessors($_) for qw( param_k1 param_b avg_doc_length );

sub new {
    my $class = shift;
    my %args  = @_;
    my $self  = $class->SUPER::new(%args);
}

sub bm25 {
    my $self = shift;
    my $text = shift;

    my $length = length($text);

    my $data = $self->_calc_tf( \$text );
    $self->_calc_idf($data);

    my $k1             = $self->param_k1       || 2.0;
    my $b              = $self->param_b        || 0.75;
    my $avg_doc_length = $self->avg_doc_length || 2000;
    my $N              = 25000000000;

    while ( my ( $key, $ref ) = each %{$data} ) {
        my $tf  = $ref->{tf};
        my $idf = log( $N / $ref->{df} );
        my $bm25 =
          $idf *
          ( $tf *
              ( $k1 + 1 ) /
              ( $tf + $k1 * ( 1 - $b + $b * ( $length / $avg_doc_length ) ) ) );
        $data->{$key}->{bm25} = $bm25;
    }

    return Lingua::JA::OkapiBM25::Result->new($data);
}

1;
__END__