function toccs(dtm, classid, name)

% toccs(dtm, classid, name)
%   convert a sparse document-term matrix in Matlab to CCS format.
%   each row of dtm is a document and each column is a dimension.
%   classid is the class labels (starting from 1 in Matlab).

[n,d] = size(dtm);
[i,j,xx] = find(dtm');
dat = unitnorm(logidf(dtm),2)';
[i,j,s] = find(dat);
j = [j; n+1];
j = diff(j);
j = find(j>0);
j = [0 ; j];

fid = fopen([name '_col_ccs'],'w');
fprintf(fid,'%d\n',j);
fclose(fid);

fid = fopen([name '_row_ccs'],'w');
fprintf(fid,'%d\n',i-1);
fclose(fid);

fid = fopen([name '_tfn_nz'],'w');
fprintf(fid,'%d\n',s);
fclose(fid);

fid = fopen([name '_txx_nz'],'w');
fprintf(fid,'%d\n',xx);
fclose(fid);

fid = fopen([name '_pattern'],'w');
fprintf(fid, '%d %d\n', n, 1);
fprintf(fid, '%d\n', classid-1);
fclose(fid);

fid = fopen([name '_dim'],'w');
fprintf(fid, '%d %d %d\n', d, n, length(xx));
fclose(fid);

return;