Please help package Search::VectorSpace; problem


O

Ohm

Iam tring to create a search tool using PDL andVectorSpace.
doc1.txt and doc2.txt are files with some text in it.
Appreciate any help here, as Iam not very good in Perl.


Error Iam getting is:
Making word list:
Use of uninitialized value in subroutine entry at
C:/Perl/site/lib/Search/Vector
Space.pm line 175, <DATA> line 584.
Finished with word list
Can't locate object method "set_threshold" via package
"Search::VectorSpace" at
search.pl line 13, <DATA> line 584.

======================================
#search.pl
use Search::VectorSpace;

#my @docs = get_documents_from_somewhere();
my @docs = {'doc1.txt', 'doc2.txt'};


my $engine = Search::VectorSpace->new( docs => \@docs );


$engine->build_index();
$engine->set_threshold( '0.01' );


while ( my $query = <> ) {
my %results = $engine->search( $query );
foreach my $result ( sort { $results{$b} <=> $results{$a} }
keys %results ) {
print "Relevance: ", $results{$result}, "\n";
print $result, "\n\n";
}


print "Next query?\n";
}



=======================================
package Search::VectorSpace;

use warnings;
use strict;
use Lingua::Stem;
use Carp;
use PDL;

our $VERSION = '0.02';

=head1 TITLE

Search::VectorSpace - a very basic vector-space search engine

=head1 SYNOPSIS

use Search::VectorSpace;

my @docs = ...;
my $engine = Search::VectorSpace->new( docs => \@docs, threshold =>
..04);
$engine->build_index();

while ( my $query = <> ) {
my %results = $engine->search( $query );
print join "\n", keys %results;
}

=head1 DESCRIPTION

This module takes a list of documents (in English) and builds a simple
in-memory
search engine using a vector space model. Documents are stored as PDL
objects,
and after the initial indexing phase, the search should be very fast.
This
implementation applies a rudimentary stop list to filter out very
common words, and
uses a cosine measure to calculate document similarity. All documents
above
a user-configurable similarity threshold are returned.

=head1 METHODS

=over

=item new docs => ARRAYREF [, threshold => VALUE ]

Object constructor. Argument hash must contain a key 'docs' whose
value is a reference
to an array of documents. The hash can also contain an optional
threshold setting,
between zero and one, to serve as a relevance cutoff for search
results.

=cut

sub new {
my ( $class, %params ) = @_;
croak 'Usage: Search::VectorSpace->new( docs => \@docs);' unless
exists ( $params{'docs'} ) and
ref( $params{'docs'} ) and
ref( $params{'docs'}) eq 'ARRAY';

my $self =
{
docs => $params{'docs'},
threshold => $params{'threshold'} || .001,
stop_list => load_stop_list(),
};

return bless $self, $class;
}

=item build_index

Creates the document vectors and stores them in memory, along with a
master
word list for the document collection.

=cut

sub build_index() {
my ( $self ) = @_;
print "Making word list:\n";
$self->make_word_list();
my @vecs;
foreach my $doc ( @{ $self->{'docs'} }) {
my $vec = $self->make_vector( $doc );
push @vecs, norm $vec;
}
$self->{'doc_vectors'} = \@vecs;
print "Finished with word list\n";
}

=item search QUERY

Returns all documents matching the QUERY string above the set relevance
threshold.
Unlike regular search engines, the query can be arbitrarily long, and
contain
pretty much anything. It gets mapped into a query vector just like the
documents
in the collection were.
Returns a hash in the form RESULT => RELEVANCE, where the relevance
value is between
zero and one.

=cut

sub search {
my ( $self, $query ) = @_;
my $qvec = $self->make_vector( $query );

my %result_list = $self->get_cosines( norm $qvec );
my %documents;
foreach my $index ( keys %result_list ) {
my $doc = $self->{'docs'}->[$index];
my $relevance = $result_list{$index};
$documents{$doc} = $relevance;
}
return %documents;
}

=item get_words STRING

Rudimentary parser, splits string on whitespace and removes
punctuation.
Returns a hash in the form WORD => NUMBER, where NUMBER is how many
times
the word was found.

=cut

sub get_words {

# Splits on whitespace and strips some punctuation
my ( $self, $text ) = @_;
my %doc_words;
my @words = map { stem($_) }
grep { !( exists $self->{'stop_list'}->{$_} ) }
map { lc($_) }
map { $_ =~/([a-z\-']+)/i}
split /\s+/, $text;
do { $_++ } for @doc_words{@words};
return %doc_words;
}

=item stem WORD

Convenience wrapper for Lingua::Stem::stem()

=cut

sub stem {
my ( $word) = @_;
my $stemref = Lingua::Stem::stem( $word );
return $stemref->[0];
}


sub make_word_list {
my ( $self ) = @_;
my %all_words;
foreach my $doc ( @{ $self->{docs} } ) {
my %words = $self->get_words( $doc );
foreach my $k ( keys %words ) {
#print "Word: $k\n";
$all_words{$k} += $words{$k};
}
}

# create a lookup hash of word to position
my %lookup;
my @sorted_words = sort keys %all_words;
@lookup{@sorted_words} = (1..$#sorted_words );

$self->{'word_index'} = \%lookup;
$self->{'word_list'} = \@sorted_words;
$self->{'word_count'} = scalar @sorted_words;
}

sub make_vector {
my ( $self, $doc ) = @_;
my %words = $self->get_words( $doc );
my $vector = zeroes $self->{'word_count'};

foreach my $w ( keys %words ) {
my $value = $words{$w};
my $offset = $self->{'word_index'}->{$w};
index( $vector, $offset ) .= $value;
}
return $vector;
}


sub get_cosines {
my ( $self, $query_vec ) = @_;
my %cosines;
my $index = 0;
foreach my $vec ( @{ $self->{'doc_vectors'} }) {
my $cosine = cosine( $vec, $query_vec );
$cosines{$index} = $cosine if $cosine > $self->{'threshold'};
$index++;
}
return %cosines;
}

# Assumes both incoming vectors are normalized
sub cosine {
my ( $vec1, $vec2 ) = @_;
my $cos = inner( $vec1, $vec2 ); # inner product
return $cos->sclr(); # converts PDL object to Perl scalar
}


sub load_stop_list {
my %stop_words;
while (<DATA>) {
chomp;
$stop_words{$_}++;
}
return \%stop_words;
}



1;

=back

=head1 AUTHOR

Maciej Ceglowski <[email protected]>

This program is free software, released under the GNU public license

=cut

__DATA__

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A

A. Sinan Unur

Iam tring to create a search tool using PDL andVectorSpace.
doc1.txt and doc2.txt are files with some text in it.
Appreciate any help here, as Iam not very good in Perl.

Please do read the posting guidelines for this group.

Why do you think it is useful to post the code for Search::VectorSpace?

Why do you think anyone would be willing to read 870 lines?
Can't locate object method "set_threshold" via package
"Search::VectorSpace" at

When I look at the documentation for Search::VectorSpace, I do not see a
method set_threshold as part of the public interface of the module.

Instead, it looks like you have to specify the threshold in the
constructor invocation.

How is this error unexpected?

Sinan
 
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T

Tad McClellan

Ohm said:
Appreciate any help here, as Iam not very good in Perl.


Have you seen the Posting Guidelines that are posted here frequently?

Use of uninitialized value in subroutine entry at
C:/Perl/site/lib/Search/Vector
Space.pm line 175, <DATA> line 584.


You really expect potential answerers to count down to
figure out which is line number 175?

Have you looked at line number 584 of your input data to see if it
contains something your program is not prepared to deal with?

Looks like a blank line to me...

my @docs = {'doc1.txt', 'doc2.txt'};


Why are you storing a single hash ref in @docs with a key
of 'doc1.txt' and a value of 'doc2.txt' ?

my @docs = ('doc1.txt', 'doc2.txt');

Curliness matters. <g>



[snip a whole lotta code]
 

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