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Text::NSP::Measures::2UserIContributed Perl DocuText::NSP::Measures::2D::MI(3)

NAME
       Text::NSP::Measures::2D::MI - Perl module that provides error checks
				     for Loglikelihood,	Total Mutual
				     Information, Pointwise Mutual Information
				     and Poisson-Stirling Measure.

SYNOPSIS
       Basic Usage

	 use Text::NSP::Measures::2D::MI::ll;

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

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

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

DESCRIPTION
       This module is the base class for the Loglikelihood, Total Mutual
       Information and the Pointwise Mutual Information	measures. All these
       measure are similar. This module	provides error checks specific for
       these measures, it also implements the computations that	are common to
       these measures.

       Log-Likelihood measure is computed as
	   Log-Likelihood = 2 *	[n11 * log(n11/m11) + n12 * log(n12/m12) +
			    n21	* log(n21/m21) + n22 * log(n22/m22)]

       Total Mutual Information
	   TMI =   (1/npp)*[n11	* log(n11/m11)/log 2 + n12 * log(n12/m12)/log
	   2 +
			    n21	* log(n21/m21)/log 2 + n22 * log(n22/m22)/log
	   2]

       Pointwise Mutual	Information
	   PMI =   log (n11/m11)/log 2

       Poisson Stirling	Measures
	   PS =	  n11*(log (n11/m11)-1)

       All these methods use the ratio of the observed values to expected
       values, for computations, and thus have common error checks, so they
       have been grouped together.

   Methods
       getValues() - This method calls the computeMarginalTotals(),
       computeObservedValues() and the computeExpectedValues() methods to
       compute the observed and	expected values. It checks these values	for
       any errors that might cause the Loglikelihood, TMI & PMI	measures to
       fail.
	   INPUT PARAMS	 : $count_values	   .. Reference	of an hash
	   containing
						      the count	values
	   computed by the
						      count.pl program.

	   RETURN VALUES : 1/undef	     ..returns '1' to indicate success
					       and an undefined(NULL) value to
	   indicate
					       failure.

       computePMI() - Computes the pmi of a given observed and expected	value
       pair.
	   INPUT PARAMS	 : $n	      ..Observed value
			   $m	      ..Expected value

	   RETURN VALUES : log(n/m)   ..the log	of the ratio of
					observed value to expected
					value.

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: MI.pm,v 1.27 2008/03/26 17:18:26 tpederse Exp	$

BUGS
SEE ALSO
       <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.

perl v5.32.0			  2008-03-26	Text::NSP::Measures::2D::MI(3)

NAME | SYNOPSIS | DESCRIPTION | AUTHOR | HISTORY | BUGS | SEE ALSO | COPYRIGHT

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