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Re: st: create local macros named after the values of a categorial variable

From   Maarten buis <>
Subject   Re: st: create local macros named after the values of a categorial variable
Date   Fri, 13 Aug 2010 13:58:01 +0000 (GMT)

--- On Fri, 13/8/10, Oliver Jones wrote:
> The -collapse- command is not going to work for me because
> of its vast need of memory, see my post:
> "RE: st: RE: collapse is too memory demanding"
> from Tue, 27 Jul 2010.
> The workaround is working but is quite slow, it took about
> 20 hours to complete. That's why I'm thinking of a way to
> program more efficient.

Maybe the variation on -collapse- in the example below solves
your problem?

*----------------- begin example ------------------
// create some example data
// the gr* variables are your group variables (like your city_code)
// the x* variables are the variables you want to count
drop _all
set obs 1000 
gen long id = _n

gen gr1 = ceil(3*runiform())
gen gr2 = ceil(3*runiform())
gen gr3 = ceil(3*runiform())

gen x1 = runiform() < .2
gen x2 = runiform() < .5
gen x3 = runiform() < .7

// sort on your grouping variables and finaly your id
sort gr1 gr2 gr3 id

// create a variable indicating the last observation within a group
by gr1 gr2 gr3 : gen byte last = _n == _N

// store the counts of the first variable in a mata matrix counts
// notice that the number of rows in this matrix equals the number 
// of groups not the number of observations
by gr1 gr2 gr3 : gen long count = sum(x1)
mata : counts = st_data(. , ("count"), "last")

// loop over the remaining variables
// if the variable names are not so nicely regular you can just
// loop over them using -foreach-
forvalues i = 2/3 {
	by gr1 gr2 gr3 : replace count = sum(x`i')
	mata : counts = counts, st_data(. , "count", "last")

// keep one observation per group and 
// keep only your grouping variables
keep if last
keep gr1 gr2 gr3

// store the matrix of counts
idx = st_addvar(("long","long", "long"), ("count1","count2", "count3"))
st_store(., idx, counts)

// display the results
*------------------- end example --------------------------
(For more on examples I sent to the Statalist see: )

Hope this helps,

Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen


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