Text::NSP::Measures::3D::MI - Perl module that provides error checks and framework to implement Loglikelihood, Total Mutual Information, Pointwise Mutual Information and Poisson Stirling Measure for trigrams.
use Text::NSP::Measures::3D::MI::ll; $ll_value = calculateStatistic( n111=>10, n1pp=>40, np1p=>45, npp1=>42, n11p=>20, n1p1=>23, np11=>21, nppp=>100); if( ($errorCode = getErrorCode())) { print STDERR $erroCode." - ".getErrorMessage()."\n"; } else { print getStatisticName."value for bigram is ".$ll_value."\n"; }
This module is the base class for the Loglikelihood and the True 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 = 2 * [n111 * log(n111/m111) + n112 * log(n112/m112) + n121 * log(n121/m121) + n122 * log(n122/m122) + n211 * log(n211/m211) + n212 * log(n212/m212) + n221 * log(n221/m221) + n222 * log(n222/m222)]
tmi = [n111/nppp * log(n111/m111) + n112/nppp * log(n112/m112) + n121/nppp * log(n121/m121) + n122/nppp * log(n122/m122) + n211/nppp * log(n211/m211) + n212/nppp * log(n212/m212) + n221/nppp * log(n221/m221) + n222/nppp * log(n222/m222)]
pmi = log (n111/m111)
ps = n111 * ( log(n111/m111) - 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.
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.
INPUT PARAMS : $n ..Observed value $m ..Expected value
RETURN VALUES : lognm .. the log of the ratio of observed value to expected value.
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: MI.pm,v 1.15 2008/03/26 17:41:33 tpederse Exp $
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http://www.d.umn.edu/~tpederse/nsp.html
Copyright (C) 2000-2006, Ted Pedersen, Satanjeev Banerjee, Amruta Purandare, Bridget Thomson-McInnes and Saiyam Kohli
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