discretisation.m

this program is to layer the given image by natural cutting developed by using c

function [EigenvectorsDiscrete,EigenVectors]=discretisation(EigenVectors)
% 
% EigenvectorsDiscrete=discretisation(EigenVectors)
% 
% Input: EigenVectors = continuous Ncut vector, size = ndata x nbEigenvectors 
% Output EigenvectorsDiscrete = discrete Ncut vector, size = ndata x nbEigenvectors
%
% Timothee Cour, Stella Yu, Jianbo Shi, 2004

[n,k]=size(EigenVectors);

vm = sqrt(sum(EigenVectors.*EigenVectors,2));
EigenVectors = EigenVectors./repmat(vm,1,k);

R=zeros(k);
R(:,1)=EigenVectors(1+round(rand(1)*(n-1)),:)';
c=zeros(n,1);
for j=2:k
    c=c+abs(EigenVectors*R(:,j-1));
    [minimum,i]=min(c);
    R(:,j)=EigenVectors(i,:)';
end

lastObjectiveValue=0;
exitLoop=0;
nbIterationsDiscretisation = 0;
nbIterationsDiscretisationMax = 20;%voir
while exitLoop== 0 
    nbIterationsDiscretisation = nbIterationsDiscretisation + 1 ;   
    EigenvectorsDiscrete = discretisationEigenVectorData(EigenVectors*R);
    [U,S,V] = svd(EigenvectorsDiscrete'*EigenVectors,0);    
    NcutValue=2*(n-trace(S));
    
    if abs(NcutValue-lastObjectiveValue) < eps | nbIterationsDiscretisation > nbIterationsDiscretisationMax
        exitLoop=1;
    else
        lastObjectiveValue = NcutValue;
        R=V*U';
    end
end