Dear GRETL listers, greetings from Paris ! I am currently working on 3-goods demand systems and I need to use matrix operations to compute price and income elasticities. However I find it difficult to define the matrix of three different ols models named say m1, m2, m3. More precisely, I would to define the matrix : Z = {m1.$coeff;m2.$coeff;m3.$coeff} but this does not work because this is not allowed with matrices (chap 16) but only scalars. So I defined submatrixes : z1 = m1.$coeff etc. but the problem persists: I cant form a matrix with those three vectors. I would like to know if it is possible to build such a matrix by staking vectors or if the present case I must use simultaneous equations specifying OLS directly to recover $coeff as a matrix. Sincerly Franck