Re: [Gretl-users] 2 questions

Dear Jack, thanks for your answer. I will try to be more specific on the second answer. I have a panel data of price of several goods (variables) for supermarkets (units) at different time. Also, I have information for to wich city it belong each supermarket. I need to calculate several means: 1) for each good, then for each city, and then for each day, the mean price for all supermarkets that post the price that day. 2) forget goods for the moment. I first restrict the sample by city, and then by time (as I generate a time dummy for each day) 3) for each time and city I want to calculate the mean price, so I made the following script: smpl full genr time genr veces = d_prod_1 <> 0 discrete ciudad smpl time <3 --restrict Mciudad = values(ciudad) Mtime = values(time) #matriz para poner las medias de cada estimacion matrix Xmean2 = Mciudad ** Mtime' matrix Xmean = Xmean2 - Xmean2 #matriz para calcular la media y desviación estandar loop i=1..rows(Mciudad) scalar xi = Mciudad[i] smpl (ciudad=xi) --restrict --replace loop j=1..rows(Mtime) scalar tj = Mtime[j] smpl (time=tj) --restrict --replace find = {$i;$j} scalar m = mean(veces) subst = {m} X = replace(Xmean, find, subst) printf "mean(veces | ciudad = %g | time = %g) = %8.5f, sd(veces | ciudad = %g | time = %g) = %g\n", \ xi, tj, mean(veces), xi, tj, sd(veces) end loop end loop 4) I generate a matrix which rows are the (number of) city and columns the time moment. Mciudad = values(ciudad) Mtime = values(time) #matriz para poner las medias de cada estimacion matrix Xmean2 = Mciudad ** Mtime' matrix Xmean = Xmean2 - Xmean2 5) Now I want to store in the ith jth element of the matrix, the mean of the ith city at the jht moment of time, so I try this, which is wrong I supposse: find = {$i;$j} scalar m = mean(veces) subst = {m} X = replace(Xmean, find, subst) Is there any way to store the iht jth calculation of the mean in the matrix I created in that position? Thanks, and I hope to be more clear now Leandro 2011/6/6 Riccardo (Jack) Lucchetti <r.lucchetti(a)univpm.it&gt;