[Gretl-users] Re: Reverse a cross tabulation or frequency table

On 04/08/2023 20:24, Josué Martínez-Castillo wrote: > Thank you both, Artur and sven. Both approaches were very helpful. I > finally used: > >> _ _ >> # mymatrix: column1 = income, column2 = frequency >> matrix mymatrix = {35, 5; 120, 5; 150, 0; 320, 6; 400, 5} >> matrix result = {} >> loop i=1..5 >> result |= mshape(mymatrix[i,1], mymatrix[i,2], 1) >> endloop >> print mymatrix result >> _ _ The best generalisation I could find to the 2-way (xtab) case is as follows: <hansl> set seed 1234567 nr = 3 nc = 2 ### xtab case xt = mrandgen(i, 0, 6, nr, nc) tot = nr * nc result = zeros(sum(xt), 2) fin = 0 loop j = 1 .. nc loop i = 1 .. nr x = xt[i,j] if x > 0 ini = fin+1 fin += x result[ini:fin,] = mshape({i,j}, 2, x)' endif endloop endloop print xt result </hansl> On the other hand, Sven's remark made me think that sometimes you might want to compute all possible indices of a arbitrarily-sized tensor. Once you have those, you can use them in a single loop without having to nest many. The function is: <hansl> function matrix indices(matrix dims) n = nelem(dims) if n == 0 ret = {} elif n == 1 ret = seq(1, dims[1])' else matrix a = indices(dims[-1]) scalar d = dims[1] scalar m = rows(a) b = vec(mshape(seq(1,d), d, m)') a = ones(d,1) ** a ret = b ~ a endif return ret end function </hansl> So for example, you can create X = indices({2,3}), which would yield 1 1 1 2 1 3 2 1 2 2 2 3 and loop over the rows of X instead of a nested loop construct such as <hansl> loop i = 1 .. 2 loop j = 1 .. 3 # do things endloop endloop </hansl> The nice thing is, the number of elements in the argument to the "indices" function is potentially unlimited. For example, indices({3,2,3}) returns 1 1 1 1 1 2 1 1 3 1 2 1 1 2 2 1 2 3 2 1 1 2 1 2 2 1 3 2 2 1 2 2 2 2 2 3 3 1 1 3 1 2 3 1 3 3 2 1 3 2 2 3 2 3 Maybe we could add this to the extra addon? ------------------------------------------------------- Riccardo (Jack) Lucchetti Dipartimento di Scienze Economiche e Sociali (DiSES) Università Politecnica delle Marche (formerly known as Università di Ancona) r.lucchetti(a)univpm.it http://www2.econ.univpm.it/servizi/hpp/lucchetti ------------------------------------------------------- _______________________________________________ Gretl-users mailing list -- gretl-users(a)gretlml.univpm.it To unsubscribe send an email to gretl-users-leave(a)gretlml.univpm.it Website: https://gretlml.univpm.it/postorius/lists/gretl-users.gretlml.univpm.it/