Thanks to all who have responded on my question!! I am on vacation
now, so I shall try out your suggestions when I'm back, in a week.
On 8/3/05, n j cox <[email protected]> wrote:
> Jeppe Warberg Larsen asked (minor editing here)
>
> > I have a wide data structure. Each observation consists of a unique
> > identifier (say, -id-) and some series of annual variables with a
> > two-digit suffix (running in different intervals). Like this:
> >
> > id var1_88 var1_89 ... var1_02 var2_92 var2_93 ... var2_02
> > var3_...................................
>
> > Now I want to -reshape- it to long, but Stata fails to read the
> > two-digit values after the turn of century (00 01 02), so I need to
> > -rename- all varibles to a four-digit year.
>
> and then later admitted
>
> > the variable names are not actually var1_ var2_ var3_ ... but words:
> > something_ somethingelse_
>
> Jeppe got various good advice from Rafa De Hoyos, David Harrison, Philip
> Ryan and James Muller. Leaving on one side a direct -reshape- solution,
> interesting in its own right, but not the main issue here,
> the emphasis was on how to set up a -foreach- loop. Something like
> this is indicated (this code owes most to David Harrison's solution,
> but replaces an -if-/-else- construct by a call to -cond()-):
>
> foreach v of varlist *_?? {
> local yy = substr("`v'",-2,2)
> local cc = cond(`yy' < 50, 20, 19)
> local new = substr("`v'",1,length("`v'")-2) + "`cc'`yy'"
> rename `v' `new'
> }
>
> I was also interested to see whether -renvars- from STB-61, which
> purports to offer canned solutions to many renaming problems, was
> up to the job.
>
> There may be a simpler way, but a somewhat grotesque one-line solution
> is possible with -renvars-, here split for display.
>
> renvars *_??, map(substr("@",1,length("@")-2) + cond(substr("@",-2,2)
> < "50", "20" + substr("@",-2,2),
> "19" + substr("@",-2,2)))
>
> A detail of note is the use of -cond()- in both solutions. In the
> first case, it is optional but replaces up to 6 lines with one.
> In the second case, it is essential as no -if-/-else- construct
> can be put inside the -map()- option of -renvars-.
>
> The next issue of the Stata Journal will carry a tutorial on -cond()-
> by David Kantor and myself, as it often seems to be overlooked
> in problems like these.
>
> Personally, I prefer the -foreach- route here. Brevity is good,
> but clarity is more important. I find it easier to follow the
> -foreach- logic step by step than to decode a complicated all-in-one
> solution.
>
> Nick
> [email protected]
>
>
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