xy2libsvm.m

将二维数据转换成libsvm格式的程序

function xy2svmlight(data,file_name)
% XY2LIBSVM Converts data set to LIBSVM format.
%
% Synopsis:
%  xy2libsvm(data,file_name).
%
% Description:
%  This function saves training data to text file required
%  by the LIBSVM software. 
%
% Input:
%  data.X [ num_data x dim] training data stored as column vectors.
%  data.y [ num_data x 1] labels of traning data; possible values 
%   are 1 (first class) and 2 (second class).
%
% Output:
%  Text file 'file_name' in LIBSVM format.
%
% See also XY2SVMLIGHT.
%

% 20-Aug-2007, Freda, created

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

dim=size(data.X,2);
num_data=size(data.X,1);

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

for i=1:num_data,

  if data.y(i) == 1, 
    fprintf(fid,'+1 '); 
  elseif data.y(i) == 2,
    fprintf(fid,'-1 '); 
  else
    fprintf(fid,'0 '); 
  end      
  
  txt(inx2) = data.X(i,:);
  
  fprintf( fid, '%d:%f ', txt );
  fprintf(fid,'\n');
end

fclose(fid);

return;