Text::NSP::Measures::2D::odds.3pm

Langue: en

Version: 2006-06-21 (mandriva - 01/05/08)

Section: 3 (Bibliothèques de fonctions)

Sommaire

NAME

Text::NSP::Measures::2D::odds - Perl module to compute the Odds
                                ratio for bigrams.

SYNOPSIS

Basic Usage 
  use Text::NSP::Measures::2D::odds;
 
 

   my $npp = 60; my $n1p = 20; my $np1 = 20;  my $n11 = 10;
 
 

   $odds_value = calculateStatistic( n11=>$n11,
                                       n1p=>$n1p,
                                       np1=>$np1,
                                       npp=>$npp);
 
 

   if( ($errorCode = getErrorCode()))
   {
     print STDERR $errorCode." - ".getErrorMessage()."\n"";
   }
   else
   {
     print getStatisticName."value for bigram is ".$odds_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 odds ratio computes the ratio of the number of times that the words in a bigram occur together (or not at all) to the number of times the words occur individually. It is the cross product of the diagonal and the off-diagonal.

Thus, ODDS RATIO = n11*n22/n21*n12

if n21 and/or n12 is 0, then each zero value is ``smoothed'' to one to avoid a zero in the denominator.

calculateStatistic() - method to calculate the odds ratio value!
INPUT PARAMS : $count_values .. Reference of an hash containing
                                       the count values computed by the
                                       count.pl program.

RETURN VALUES : $odds .. Odds ratio 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: odds.pm,v 1.18 2006/06/21 11:10:52 saiyam_kohli Exp $

BUGS

SEE ALSO

   @inproceedings{ blaheta01unsupervised,
                   author = {D. BLAHETA and M. JOHNSON},
                   title = {Unsupervised learning of multi-word verbs},
                   booktitle = {}Proceedings of the 39th Annual Meeting of the ACL},
                   year = {2001},
                   pages =  {54-60},
                   url = L<http://www.cog.brown.edu/~mj/papers/2001/dpb-colloc01.pdf> }

<http://groups.yahoo.com/group/ngram/>

<http://www.d.umn.edu/~tpederse/nsp.html>

Copyright (C) 2000-2006, Ted Pedersen, Satanjeev Banerjee, Amruta Purandare, Bridget Thomson-McInnes and Saiyam Kohli

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.