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?
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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