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@univpm.it>

On Mon, 6 Jun 2011, Leandro Zipitria wrote:

If I am working with a restricted version of a variable (using smpl --restrict), the mean, standard deviation, etc. reported is for the variable as a whole or just the restricted sample?

Just the restricted sample. Example:

gretl version 1.9.5cvs
Copyright Ramu Ramanathan, Allin Cottrell and Riccardo "Jack" Lucchetti
This is free software with ABSOLUTELY NO WARRANTY
Current session: 2011-06-06 21:11

"help" gives a list of commands
Type "open filename" to open a data set
? open data4-1
open data4-1

Read datafile /usr/local/share/gretl/data/data4-1.gdt
periodicity: 1, maxobs: 14
observations range: 1-14

Listing 5 variables:
0) const 1) price 2) sqft 3) bedrms 4) baths

? m = mean(sqft)
m = mean(sqft)
Generated scalar m = 1910.93
? smpl 2 10
smpl 2 10
Full data range: 1 - 14 (n = 14)
Current sample: 2 - 10 (n = 9)

? m = mean(sqft)
m = mean(sqft)
Replaced scalar m = 1670.44

As a second answer, I am creating a doble loop for iterating mean and standar deviation from a variable. I want to create a matix that store the results of each calculation. That is, I have a panel, and want to restrict it looping on one variable (city) which will be the columns, and the time the rows. Each time gretl compute one statistic, I am trying to store it in the matrix, following the previous order. Is this possible?

Yes it is. That said, I'm not at all sure to have understood what your need is, but I have the feeling that you can write a much more efficient script by using the pmean() and psd() function. Also, the user's guide is your friend.

Riccardo (Jack) Lucchetti
Dipartimento di Economia
Università Politecnica delle Marche

r.lucchetti@univpm.it
http://www.econ.univpm.it/lucchetti
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