NAME

Text::NSP::Measures::2D::Dice::jaccard - Perl module that implements
the jaccard coefficient.

SYNOPSIS

Basic Usage

  use Text::NSP::Measures::2D::Dice::jaccard;
  my $npp = 60; my $n1p = 20; my $np1 = 20;  my $n11 = 10;
  $jaccard_value = calculateStatistic( n11=>$n11,
                                      n1p=>$n1p,
                                      np1=>$np1,
                                      npp=>$npp);
  if( ($errorCode = getErrorCode()))
  {
    print STDERR $errorCode." - ".getErrorMessage()."\n"";
  }
  else
  {
    print getStatisticName."value for bigram is ".$jaccard_value."\n"";
  }

DESCRIPTION

Assume that the frequency count data associated with a bigram <word1><word2> is stored in a 2x2 contingency table:

          word2   ~word2
  word1    n11      n12 | n1p
 ~word1    n21      n22 | n2p
           --------------
           np1      np2   npp

where n11 is the number of times <word1><word2> occur together, and n12 is the number of times <word1> occurs with some word other than word2, and n1p is the number of times in total that word1 occurs as the first word in a bigram.

The Jaccard Coefficient is the ratio of number of times the words occur together to the number of times atleast any one of the words occur. It is defined as:

          n11
    ---------------
    n11 + n12 + n21

The Jaccard coefficient can also be computed by applying a transformation to the dice coefficient:

$jaccard = $dice/(2-$dice)

We use this computation of jaccard in our implementation.

Methods

calculateStatistic() - method to calculate the jaccard coefficient value: INPUT PARAMS : $count_values .. Reference of an hash containing
the count values computed by the
count.pl program.
RETURN VALUES : $jaccard .. Jaccard Coefficient value for this bigram.
getStatisticName() - Returns the name of this statistic: INPUT PARAMS : none
RETURN VALUES : $name .. Name of the measure.

AUTHOR

Ted Pedersen, University of Minnesota Duluth
<tpederse@d.umn.edu>

Satanjeev Banerjee, Carnegie Mellon University
<satanjeev@cmu.edu>

Amruta Purandare, University of Pittsburgh
<amruta@cs.pitt.edu>

Bridget Thomson-McInnes, University of Minnesota Twin Cities
<bthompson@d.umn.edu>

Saiyam Kohli, University of Minnesota Duluth
<kohli003@d.umn.edu>

HISTORY

Last updated: $Id: jaccard.pm,v 1.8 2006/06/21 11:10:52 saiyam_kohli Exp $

BUGS

COPYRIGHT

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to

    The Free Software Foundation, Inc.,
    59 Temple Place - Suite 330,
    Boston, MA  02111-1307, USA.

Note: a copy of the GNU General Public License is available on the web at <http://www.gnu.org/licenses/gpl.txt> and is included in this distribution as GPL.txt.