# -*- cperl -*-

=head1 NAME

nat-initmat - initialize a sparse matrix with words co-occurrence.

=head1 SYNOPSIS

 nat-initmat <crp1> <crp2> [<exc1> <exc2>] <matrix>

=head1 DESCRIPTION

This tool is used internally by C<nat-these> and is not intended to be
used independently. Basically, this tool takes two corpora files
created by C<nat-pre> and allocates a sparse matrix, where rows
indexes correspond to word identifiers on the source corpus, and
column indexes correspond to word identifiers on the target
corpus. Cells count the words co-occurrence on the same sentence.
The C<matrix> file is then created with the matrix information.

Optionally, you can pass to the system two exclude lists, as returned
by the C<nat-words2id> tool. These words will be ignored, and counting
will not be done for them.

The matrix is saved and can be processed later by EM-Algorithm methods
IPFP (C<nat-ipfp>), Sample A (C<nat-samplea>) and Sample B
(C<nat-sampleb>).

=head1 SEE ALSO

nat-words2id, nat-pre, NATools documentation

=head1 COPYRIGHT

 Copyright (C)2002-2009 Alberto Simoes and Jose Joao Almeida
 Copyright (C)1998 Djoerd Hiemstra

 GNU GENERAL PUBLIC LICENSE (LGPL) Version 2 (June 1991)

=cut

