x2 = 2 * [((n11 - m11)/m11)^2 + ((n12 - m12)/m12)^2 + ((n21 - m21)/m21)^2 + ((n22 -m22)/m22)^2]
PHI^2 = ((n11 * n22) - (n21 * n21))^2/(n1p * np1 * np2 * n2p)
tscore = (n11 - m11)/sqrt(n11)
Chi-Squared = npp * PHI^2
Although T-score seems quite different from the other two measures we
have put it in the CHI family because like the other two measures it
uses the difference between the observed and expected values and is also
quite similar in ranking the bigrams.
|getValues() - This method calls the computeMarginalTotals(), computeObservedValues() and the computeExpectedValues() methods to compute the observed and expected values. It checks thees values for any errors that might cause the PHI and x2 measures to fail.||
INPUT PARAMS : $count_values .. Reference of an hash containing
the count values computed by the
RETURN VALUES : 1/undef ..returns 1 to indicate success
|computeVal() - Computes the deviation in observed value with respect to the expected values||
INPUT PARAMS : $n ..Observed value
$m ..Expected value
RETURN VALUES : (n-m)^2/m ..the log of the ratio of
Ted Pedersen, University of Minnesota Duluth
Satanjeev Banerjee, Carnegie Mellon University
Amruta Purandare, University of Pittsburgh
Bridget Thomson-McInnes, University of Minnesota Twin Cities
Saiyam Kohli, University of Minnesota Duluth
Last updated: $Id: CHI.pm,v 1.14 2008/03/26 17:18:26 tpederse Exp $
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 v5.20.3||TEXT::NSP::MEASURES::2D::CHI (3)||2008-03-26|