Bridget McInnes > Text-NSP-1.21 > Text::NSP::Measures::2D::odds



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


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,

  if( ($errorCode = getErrorCode()))
    print STDERR $errorCode." - ".getErrorMessage()."\n"";
    print getStatisticName."value for bigram is ".$odds_value."\n"";


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 program.

RETURN VALUES : $odds .. Odds ratio for this bigram.

getStatisticName() - Returns the name of this statistic


RETURN VALUES : $name .. Name of the measure.


Ted Pedersen, University of Minnesota Duluth <>

Satanjeev Banerjee, Carnegie Mellon University <>

Amruta Purandare, University of Pittsburgh <>

Bridget Thomson-McInnes, University of Minnesota Twin Cities <>

Saiyam Kohli, University of Minnesota Duluth <>


Last updated: $Id:,v 1.18 2006/06/21 11:10:52 saiyam_kohli Exp $



  @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<> }


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 and is included in this distribution as GPL.txt.

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