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k_ssmd_train.m
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k_ssmd_train.m
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function model = k_ssmd_train(X,Y,model)
% K_SSMD_TRAIN Kernel Selective Sampling Mistake Driven
%
% MODEL = K_SSMD_TRAIN(X,Y,MODEL) trains an classifier according to the
% Selective Sampling Mistake Driven algorithm, using kernels. The
% algorithm will query a label only on certain rounds.
%
% Additional parameters:
% - model.K is the parameter to tune the query rate.
% Default value is 1.
%
% References:
% - Cavallanti, G., Cesa-Bianchi, N., & Gentile, C. (2011)
% Learning noisy linear classifiers via adaptive and selective sampling
% Machine Learning, 83, (pp. 71-102).
% This file is part of the DOGMA library for MATLAB.
% Copyright (C) 2009-2011, Francesco Orabona
%
% 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 3 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, see <http://www.gnu.org/licenses/>.
%
% Contact the author: francesco [at] orabona.com
n = length(Y); % number of training samples
if isfield(model,'iter')==0
model.iter=0;
model.beta=[];
model.beta2=[];
model.errTot=0;
model.numSV=zeros(numel(Y),1);
model.aer=zeros(numel(Y),1);
model.pred=zeros(numel(Y),1);
model.Kinv=0;
model.Y_S=[];
model.N=0;
model.numQueries=0;
model.nacr=zeros(numel(Y),1);
end
if isfield(model,'K')==0
model.K=1;
end
for i=1:n
model.iter=model.iter+1;
if numel(model.S)>0
if isempty(model.ker)
K_f=X(model.S,i);
Kii=X(i,i);
else
K_f=feval(model.ker,model.SV,X(:,i),model.kerparam);
Kii=feval(model.ker,X(:,i),X(:,i),model.kerparam);
end
val_f=model.beta*K_f;
else
if isempty(model.ker)
Kii=X(i,i);
else
Kii=feval(model.ker,X(:,i),X(:,i),model.kerparam);
end
val_f=0;
K_f=0;
end
Yi=Y(i);
model.errTot=model.errTot+(sign(val_f)~=Yi);
model.aer(model.iter)=model.errTot/model.iter;
model.nacr(model.iter)=(model.iter-model.errTot)/model.numQueries;
coeff=K_f'*model.Kinv;
delta=Kii-coeff*K_f;
val_f=val_f/(delta+1);
model.pred(model.iter)=val_f;
if val_f^2<=Kii*model.K*log(model.iter)/model.N
model.numQueries=model.numQueries+1;
if val_f*Yi<=0
model.S(end+1)=model.iter;
if ~isempty(model.ker)
model.SV(:,end+1)=X(:,i);
end
model.Y_S(end+1)=Yi;
if numel(model.S)>1
tmp=[model.Kinv, zeros(numel(model.S)-1,1);zeros(1,numel(model.S))];
tmp=tmp+[coeff'; -1]*[coeff'; -1]'/(delta+1);
else
tmp=full((Kii+1)^-1);
end
model.Kinv=tmp;
model.beta=model.Y_S*model.Kinv;
model.N=model.N+1;
end
end
model.numSV(model.iter)=numel(model.S);
if mod(i,model.step)==0
fprintf('#%.0f SV:%5.2f(%d)\tAER:%5.2f\tQueried Labels:%5.2f(%d)\n', ...
ceil(i/1000),numel(model.S)/model.iter*100,numel(model.S),...
model.aer(model.iter)*100,model.numQueries/model.iter*100,...
model.numQueries);
end
end