Text::NSP::Measures::2D::CHI::phi - Perl module that implements Phi coefficient measure for bigrams.
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""; }
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.
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.
INPUT PARAMS : none
RETURN VALUES : $name .. Name of the measure.
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>
Last updated: $Id: phi.pm,v 1.12 2006/06/21 11:10:52 saiyam_kohli Exp $
@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 (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.
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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.