Hi, Is there a way to reverse a frequency table? Suppose I have a matrix of two columns. The first has values for income per capita variable and the second column has the number of persons that earned each specific income. Is there a way to generate a new matrix with only one column that repeats each income per capita value by the number of persons (frequency)? Thanks. _______________________________________________ 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/

Am 04.08.2023 um 13:40 schrieb Artur Bala: Hi, You can try the following script: _ _ # mymatrix: column1 = income, column2 = frequency matrix mymatrix = {35, 5; 120, 5; 150, 0; 320, 6; 400, 5} matrix result = {} loop i=1..5 loop mymatrix[i,2] result = result | {mymatrix[i,1]} endloop endloop print mymatrix result Thanks, Artur - for larger datasets one may want to avoid the inner explicit loop and do something like: result |= mshape(mymatrix[i,1], mymatrix[i,2], 1) instead. (Or using indexing: result |= mymatrix[i,1][ones(mymatrix[i,2])] -- but untested.) I also guess that there's a clever way to avoid even the outer loop, maybe using the Kronecker product or so. In any case, this presupposes an exact frequency table for each (discrete) occurring value, while for things like income one would probably have a kind of histogram instead with bins. cheers sven _______________________________________________ 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/

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/