xi2svmlight.m

st ptool

function xi2svmlight(X,I,fname)
% XI2SVMLIGHT converts data set to SVM Light format
%   xi2svmlight(X,I,fname)
%
% Input:
%  X [DxN] N patterns of dimension D.
%  I [1xN] labels of patterns (1 - first class, 2 - second class)
%
% Output:
%  Text file in SVM_Light format.
%

% Modifications:
%  30-apr-2001, V. Franc, created

fid = fopen( fname, 'w+');

D=size(X,1);
N=size(X,2);

txt = zeros(1,2*D);
inx1 = 1:2:2*D;
txt(inx1) = 1:D;
inx2 = 2:2:2*D;

for i=1:N,

  if I(i) == 1, 
    fprintf(fid,'+1 '); 
  elseif I(i) == 2,
    fprintf(fid,'-1 '); 
  else
    fprintf(fid,'0 '); 
  end      

  
  x = X(:,i);
  txt(inx2) = X(:,i);
  
  fprintf( fid, '%d:%f ', txt );
  fprintf(fid,'\n');
  
end

fclose(fid);

return;