How can I save a very large MATLAB sparse matrix to a text file?

[i,j,val] = find(data)
data_dump = [i,j,val]

data = spconvert( data_dump )

save -ascii data.txt data_dump

fid = fopen('data.txt','w')
fprintf( fid,'%d %d %fn', data_dump )
fclose(fid)

pw=java.io.PrintWriter(java.io.FileWriter('c:\retail.txt'));
line=num2str(0:size(data,2)-1);
pw.println(line);
for index=1:length(data)
    disp(index);
    line=num2str(full(data(index,:)));
    pw.println(line);
end
pw.flush();
pw.close();

idcs = find(data);
vals = data(idcs);
...save the index vector and value vector in whatever format you want...