Dear R-help, I need help reconstructing contingency tables from (sort-of) marginals, so that I can use loglin to model the table. I'm working with category variables that are binary. However, my data have already been summed over other variables and I need to un-sum it, i.e. if my variables are A and B, I would like to have the cell (Nij) frequencies N total trials N(A=0, B=0) = N00 times N(A=0, B=1) = N01 N(A=1, B=0) = N10 N(A=1, B=1) = N11 but instead I have N(A=1) = N_1+ [summed over B], N(B=1) = N_+1 [summed over B], N(A=1, B=1) = N_11 data available to me. For 2x2 it's straightforward to compute Nij: N00 = N - N_1+ - N_+1 + N_11 N01 = N_+1 - N_11 N10 = N_1+ - N_11 N11 = N_11 and then I can use xtabs. But it gets more complicated as the number of category variables increases. I know how to do it on paper, but I don't know how to do it in a generic way within R. - Mike