function S=indexFile2CountMatrix(fname)
% function S=indexFile2CountMatrix(fname)
%
% create a spare term count matrix from an indexed file produced by
% indexCorpus.cpp.
%
% Guy Lebanon, 2005.

%figure out the vocab size and the number of distinct files
i=0;maxV=0;
fid=fopen(fname,'r');
while 1
    tline = fgetl(fid);
    if ~ischar(tline), break, end
    vec=str2num(tline);
    if ~isempty(vec), 
        M=max(vec);
        if M>maxV, maxV=M;end
    end
    i=i+1;
end
fclose(fid);
S=sparse(i,maxV+1);
fid=fopen(fname,'r');
for i=1:size(S,1),
    vec=str2num(fgetl(fid));
    if isempty(vec), continue;end
    for j=1:length(vec),
        S(i,vec(j)+1)=S(i,vec(j)+1)+1;
    end
end
fclose(fid);