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Text::NSP::Measures::2D::CHI::phi.3pm

NAME

Text::NSP::Measures::2D::CHI::phi - Perl module that implements Phi coefficient
                                    measure for bigrams.

SYNOPSIS

Basic Usage

   use Text::NSP::Measures::2D::CHI::phi;
 
 

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

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

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

DESCRIPTION

This function computes the the square of the traditional formulation of the Phi Coefficient.

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.

  PHI^2 = ((n11 * n22) - (n21 * n21))^2/(n1p * np1 * np2 * n2p)
 
 

Note that the value of PHI^2 is equivalent to Pearson's Chi-Squared test multiplied by the sample size, that is:

  Chi-Squared = npp * PHI^2
 
 

We use PHI^2 rather than PHI since PHI^2 was employed for collocation identification in:

Church, K. (1991) Concordances for Parallel Text, Seventh Annual Conference of the UW Centre for the New OED and Text Research, Oxford, England.

calculateStatistic() - method to calculate the Phi Coefficient

INPUT PARAMS : $count_values .. Reference of an hash containing
                                       the count values computed by the
                                       count.pl program.

RETURN VALUES : $phi .. phi 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: phi.pm,v 1.12 2006/06/21 11:10:52 saiyam_kohli Exp $

BUGS

SEE ALSO

   @inproceedings{GaleC91,
           author = {Gale, W. and Church, K.},
           title = {A Program for Aligning Sentences in Bilingual Corpora},
           booktitle = {Proceedings of the 29th Annual Meeting of the
                       Association for Computational Linguistics},
           address = {Berkeley, CA},
           year = {1991}
           url = L<http://www.cs.mu.oz.au/acl/J/J93/J93-1004.pdf>}
 
 

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

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

COPYRIGHT

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.