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function [ypred]=knn(xapp,yapp,valY,X,k)
%
% knn implementation
%
% USE : [ypred]=knn(xapp,yapp,valY,X,k)
%
% Vincent Guigue 08/01/03
% check nargin
if nargin<4
error('too few argumemnts');
elseif nargin<5
k=3;
else
if mod(k,2)==0
error('k must be odd');
end
end
if size(xapp,2)~=size(X,2)
error('dimension incompatibility');
end
ndim = size(xapp,2);
nptxapp = size(xapp,1);
nptX = size(X,1);
% distance de X a xapp :
mat1 = repmat(xapp, nptX,1);
%mat21 = reshape(X',1,nptX*ndim)
mat22 = repmat(X,1,nptxapp)';
mat2 = reshape(mat22 ,ndim, nptxapp*nptX)';
distance = mat1 - mat2 ;
distance = sum(distance.^2,2);
distance = reshape(distance,nptxapp,nptX);
[val kppv] = sort(distance,1);
% bilan sur les k premieres lignes
kppv = reshape(kppv(1:k,:),k*nptX,1);
Ykppv = yapp(kppv,1);
Ykppv = reshape(Ykppv,k,nptX);
% trouver le plus de reponses identique par colonne
vote = [];
for i=1:nptX
for j=1:length(valY)
vote(j,i)=size(find(Ykppv(:,i)==valY(j)),1);
end
end
[val ind]=max(vote,[],1);
ypred = valY(ind);
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