Text::NSP::Measures::3D::MI 1.03

Text::NSP::Measures::3D::MI is a Perl module that provides error checks and framework to implement Loglieklihood, Total Mutual Information, Pointwise Mutual Information and Poisson Stirling Measure for trigrams.

SYNOPSIS

Basic Usage

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 measure is computed as
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)]

Total Mutual Information

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)]

Pointwise Mutual Information

pmi = log (n111/m111)

Poisson Stirling Measure

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 togrther.