## Copyright (C) 1995, 1996, 1997 Kurt Hornik ## ## 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, 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 file. If not, write to the Free Software Foundation, ## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. ## Calculates likelihood for the ordinal logistic regression model. ## Called by logistic_regression. ## Author: Gordon K. Smyth <gks@maths.uq.oz.au> ## Adapted-By: KH <Kurt.Hornik@ci.tuwien.ac.at> ## Description: Likelihood in logistic regression function [g, g1, p, dev] ... = logistic_regression_likelihood (y, x, beta, z, z1) e = exp ([z x] * beta); e1 = exp ([z1 x] * beta); g = e ./ (1 + e); g1 = e1 ./ (1 + e1); g = max (y == max (y), g); g1 = min (y > min(y), g1); p = g - g1; dev = -2 * sum (log (p)); endfunction

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