function [y,dfce]=quadclass( X, model)% QUADCLASS Quadratic classifier.%% Synopsis:%  [y,dfce] = quadclass(X,model)%% Description:%  This function classifies input data X using quadratic%  discriminant function:%%  y(i) = argmax X(:,i)'*A(:,:,y)*X(:,i) + X(:,i)'*B(:,y) + C(y)%           y%%  where parameters A [dim x dim x nfun], B [dim x nfun]%  and model C [1 x nfun] are given in model and nfun is%  number of discriminant functions.%%  In the binary case (nfun=1) the classification rule is following%    y(i) = 1 if X(:,i)'*A*X(:,i) + X(:,i)'*B + C >= 0%           2 if X(:,i)'*A*X(:,i) + X(:,i)'*B + C < 0%  %  where A [dim x dim], B [dim x 1] and C [1x1] are parameters%  given in model.%% Input:%  X [dim x num_data] Data to be classified.%%  model [struct] Describes quadratic classifier:%   .A [dim x dim x nfun] Parameter of quadratic term.%   .B [dim x nfun] Parameter of linear term.%   .C [1 x nfun] Bias.%% Output:%  y [1 x num_data] Predicted labels.%  dfce [nfun x num_data] Values of discriminat function.%% Example:%  trn = load('riply_trn');%  tst = load('riply_tst');%  gauss_model = mlcgmm(trn);%  quad_model = bayesdf(gauss_model);%  ypred = quadclass(tst.X, quad_model);%  cerror(ypred, tst.y)%  figure; ppatterns(trn); pboundary(quad_model);%% See also %  QMAP, LIN2QUAD, LINCLASS%% About: Statistical Pattern Recognition Toolbox% (C) 1999-2003, Written by Vojtech Franc and Vaclav Hlavac% <a href="http://www.cvut.cz">Czech Technical University Prague</a>% <a href="http://www.feld.cvut.cz">Faculty of Electrical Engineering</a>% <a href="http://cmp.felk.cvut.cz">Center for Machine Perception</a>% Modifications:% 2-may-2004, VF% allow model to be gievn as a cellmodel = c2s(model);[dim, num_data] = size(X);nfun = size(model.A,3);if nfun == 1,  % binary case  dfce = sum((model.A*X).*X,1) + model.B'*X + model.C;  y = ones(1,num_data);  y(find(dfce< 0)) = 2;else  % multi-class case   dfce = zeros( nfun, num_data );    for i=1:nfun,    dfce(i,:) = sum((model.A(:,:,i)*X).*X,1) + model.B(:,i)'*X + model.C(i);  end    [dummy,y] = max( dfce );  endreturn;% EOF