Statistical library package to calculate the Odds Ratio. This package should be used with statistic.pl and rank.pl.
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.
The odds ratio computes the ratio of the number of times that the words in a bigram occur together (or not at all) to the number of times the words occur individually. It is the cross product of the diagonal and the off-diagonal.
Thus, ODDS RATIO = n11*n22/n21*n12
if n21 and/or n12 is 0, then each zero value is "smoothed" to one to avoid a zero in the denominator.
Ted Pedersen <email@example.com>
Bridget Thomson McInnes <firstname.lastname@example.org>
This measure currently only defined for bigram data stored in 2x2 contingency table.
Mailing List: http://groups.yahoo.com/ngram
Copyright 2000-2004 by Ted Pedersen
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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