I don't think you can do that with the built-in crosstab function.
Depending on the number of data elements (specifically how sparse the resulting cross table is), you might just be able to "manually" fill in the crosstable, as either a single-precision array, or as a sparse matrix.
All three techniques illustrated below:
x = single([1 1 2 3 1]);
y = single([1 2 5 3 1]);
[unique_x,ix,jx] = unique(x);
[unique_y,iy,jy] = unique(y);
% Memory-intensive double-precision cross table
table = crosstab(x,y)
% "Manually" create single-precision cross table
table_single = single(zeros(numel(unique_x),numel(unique_y)));
for ii = 1:numel(x)
table_single(jx(ii),jy(ii)) = table_single(jx(ii),jy(ii)) + 1;
end
% "Manually" create sparse cross table
table_sparse = sparse(numel(unique_x),numel(unique_y));
for ii = 1:numel(x)
table_sparse(jx(ii),jy(ii)) = table_sparse(jx(ii),jy(ii)) + 1;
end
