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Re: st: Selecting stubnames for -reshape- / macrolists


From   Philipp Rehm <philipp.rehm@gmx.de>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Selecting stubnames for -reshape- / macrolists
Date   Mon, 30 Jun 2008 18:19:27 +0200

.
Thanks, Paul.

You wrote:
"You will want to make sure that if your subscripts all look like _1, _2, _3... that you only use one of them. Grabbing *_* will give the same stubname many times."

Alas, that's exactly my problem. I need to grab *_*, because I don't know which subscripts are present or absent.

(Since this may sound a little strange, let me explain why this is so. I have a data-set with thousands of variables over a maximum of 40 years or so, in wide format. The problem is that not all variables are present for all years, which is why I prefer to grab everything and get the stubs from there).

Thanks again,
Philipp


E. Paul Wileyto wrote:

I have the following implemented as an ADO. It is what I use to grab all the name stubs for reshaping. You will want to make sure that if your subscripts all look like _1, _2, _3... that you only use one of them. Grabbing *_* will give the same stubname many times.

Paul

program define namelist

***********************************************************************
***********************************************************************
* This short program helps you define a list (global macro vlist)
* of variable name roots to aid in scripting and especially reshaping.
*
* Feel free to use wildcards in varlist. Be sure that you are only
* generating the same root once.
*
* The oldsub option describes the common subscript in the the list.
* The newsub option describes the truncated subscript to be used in
* reshaping.
* * For example: Variables rx30a_s1..rx30a_s20 all have the common root
* rx30a_s, with a numerical subscript for the repetition. To extract a
* list of roots for all survey entries, use:
*
* -namelist rx*_s1, oldsub(_s1) newsub(_s)
*
***********************************************************************
***********************************************************************

syntax varlist, [oldsub(string) newsub(string)]
global vlist "`varlist'"
if "`oldsub'" > "" & "`newsub'" > "" {
global vlist : subinstr local varlist "`oldsub'" "`newsub'" , all
}
noisily ma list vlist
end


pr9@duke.edu wrote:

.
My question is whether there is a clever way to identify the stubnames
for a -reshape-. Consider this example:

sysuse auto, clear
foreach j in 1 2 3 4 5 {
gen x_`j'=rep78+`j'
gen y_`j'=rep78-`j'
}
drop y_3
gen id=_n
keep id x_* y_*

/*
This data-set contains the following variables which I want to -reshape-:
x_1 x_2 x_3 x_4 x_5
y_1 y_2 y_4 y_5
I want to -reshape- by stubnames x_ and y_.
In my "real" data-set, I know that all variables I want to end up with
as stubnames contain an underscore (_). They all also do contain numbers
after the underscore, but there is no regular pattern there.

Now, I am generating a -macrolist- with unique stubnames, but this seems
like a detour to me, especially the loop:
*/

ds *_*
foreach v in `r(varlist)' {
local f `=regexr("`v'","[0-9]+","")'
local n `n' `f'
local n: list uniq n
}
di "*** `n' ****"
reshape long `n', i(id) j(foo)

Two questions:
1) Is there a better way to identify stubnames for a -reshape-?
2) Is there a more straightforward way to arrive at a unique macrolist
than the one I chose? In particular, something like the -regexr()-
function, but with the ability to remove all instances (not just the
first) of the regular expression. Something like -subinstr()-, but for
regular expressions.

Thank you!
Philipp


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