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AI::Categorizer::Learner::SVM - Support Vector Machine Learner

=head1 SYNOPSIS

  use AI::Categorizer::Learner::SVM;
  
  # Here $k is an AI::Categorizer::KnowledgeSet object
  
  my $l = new AI::Categorizer::Learner::SVM(...parameters...);
  $l->train(knowledge_set => $k);
  $l->save_state('filename');
  
  ... time passes ...
  
  $l = AI::Categorizer::Learner->restore_state('filename');
  while (my $document = ... ) {  # An AI::Categorizer::Document object
    my $hypothesis = $l->categorize($document);
    print "Best assigned category: ", $hypothesis->best_category, "\n";
  }

=head1 DESCRIPTION

This class implements a Support Vector Machine machine learner, using
Cory Spencer's C<Algorithm::SVM> module.  In lots of the recent
academic literature, SVMs perform very well for text categorization.

=head1 METHODS

This class inherits from the C<AI::Categorizer::Learner> class, so all
of its methods are available unless explicitly mentioned here.

=head2 new()

Creates a new SVM Learner and returns it.  In addition to the
parameters accepted by the C<AI::Categorizer::Learner> class, the
SVM subclass accepts the following parameters:

=over 4

=item svm_kernel

Specifies what type of kernel should be used when building the SVM.
Default is 'linear'.  Possible values are 'linear', 'polynomial',
'radial' and 'sigmoid'.

=back

=head2 train(knowledge_set => $k)

Trains the categorizer.  This prepares it for later use in
categorizing documents.  The C<knowledge_set> parameter must provide
an object of the class C<AI::Categorizer::KnowledgeSet> (or a subclass
thereof), populated with lots of documents and categories.  See
L<AI::Categorizer::KnowledgeSet> for the details of how to create such
an object.

=head2 categorize($document)

Returns an C<AI::Categorizer::Hypothesis> object representing the
categorizer's "best guess" about which categories the given document
should be assigned to.  See L<AI::Categorizer::Hypothesis> for more
details on how to use this object.

=head2 save_state($path)

Saves the categorizer for later use.  This method is inherited from
C<AI::Categorizer::Storable>.

=head1 AUTHOR

Ken Williams, ken@mathforum.org

=head1 COPYRIGHT

Copyright 2000-2003 Ken Williams.  All rights reserved.

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

=head1 SEE ALSO

AI::Categorizer(3), Algorithm::SVM(3)

=cut