Re: st: How to make a code faster - alternatives to egen var = concat(vars) ?,

[Antoine Terracol <terracol@univ-paris1.fr>]

Tiago,

You would have to define a -byable- -program-, such as:

capture program drop mymean
program define mymean, byable(recall)
syntax varname
marksample touse
su `varlist' if `touse'
local a= _byindex()
scalar mean`a'=r(mean)
end

sysuse auto, clear
bysort foreign rep78 : mymean price
scalar dir

Antoine

On 17/06/2010 15:47, Tiago V. Pereira wrote:
> Thanks, Antoine!
>
> But for each combinations, I want to save a local containing the r(mean).
> Is it possible to do that using -bysort-?
>
> Tiago
>
>
> ---------------
> Dear statalisters,
>
> I am working on a stata code, and I need some advice.
>
> I have n categorical variables that assumes values equal to 0, 1 or 2.  My
> objective is to summarize a continuous variable (say, age) by all possible
> combinations of these categorical variables.
>
>
> For example, suppose I have 5 categorical variables (x1, x2, x3, x4 and x5):
>
>
> sum age if x1==0&x2==0&x3==0&x4==0&x5==0
>
> then
>
> sum age if x1==0&x2==0&x3==0&x4==0&x5==1
>
> then
>
> sum age if x1==0&x2==0&x3==0&x4==0&x5==2
>
> and so forth.
>
>
> What I am doing is the following: (1) I generate a string of the
> categorical variables
>
> egen combination = concat(x1 x2 x3 x4 x5)
>
> (2) convert them to numeric
>
> encode combination, gene (y)
>
> and loop over the values of the new variable y to summarize the continuous
> variable
>
> forvalues i = 1/`some_max_value' {
>
> sum age if y=`i'
>
> }
>
> This naïve solution works very well for small samples (_N<1000) and small
> number of categorical variables (5 to 7). But when I need investigate in a
> larger sample with a larger number of categorical variables, this code is
> highly inefficient (e.g. slow).
>
> Do you have any suggestions to make this procedure faster in larger data
> sets?
>
> Thanks in advance!
>
> Tiago
>
>
>
>
>
>
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