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Re: st: creating new id variable


From   "Joseph Coveney" <jcoveney@bigplanet.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: creating new id variable
Date   Tue, 28 Aug 2012 20:18:59 +0900

Nick Cox wrote:

Second example should have been

 gen newid = cond(id1 < 10, "0" + string(id1), string(id1)) + cond(id2
> < 10, "0" + string(id2), string(id2))

--------------------------------------------------------------------------------

Just to mention an alternative when converting numerical components to a single
string ID, I like to use something like

    generate str newid = string(id1, "02.0f") + string(id2, "02.0f")

I find it a little easier to code.  Adjust the format expressions based upon the
maxima of the numerical components, keeping in mind that as the size increases,
a delimiter (hyphen or space) very much helps with readability:

    generate str newid = string(id1, "03.0f") + "-" + string(id2, "04.0f")

In addition, for concatenating string numerals, -substr()- might be a slightly
easier alternative for those who come to Stata with experience of left() and
right() string functions in other languages:

    generate str newid = substr("0" + id1, -2, 2) + substr("0" + id2, -2, 2)

Joseph Coveney


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