To back up Gary: the solutions are indeed complementary.
As several people pointed out, the key is to convert the
name of the variable to lower case, not its values (which
would not even make sense if the variable was numeric).
-renvars- is a canned solution: how to use it should be clear
from the help. If not, the authors did a lousy job.
A -foreach- loop can be written on the fly, but for this
problem and for many others requires some fluency with
Stata functions, or recourse to the help. Also, Gary's
code can be stream-lined, possibly at the cost of some clarity:
foreach v of var * {
capture rename `v' `=lower("`v'")'
}
That's my favourite solution to the problem posed --
so long as you know all the syntax used -- and unless
you're a Stata programmer, you could very easily be
unfamiliar with one or more of -foreach-, local macros,
-capture- and expansion operators.
A problem with -renvars- is that it doesn't collapse
to -rename- as a special case. That is, it doesn't
allow the syntax
. renvars oldname newname
Indeed, a bunch of Stata ultra-heavyweights (1 President +
2 Vice-Presidents) once rightly disparaged -renvars- for its
"arbitrary syntax", although they didn't say what its syntax
_should_ be.
So let's try that. Start with -rename-, and redesign it to
cope with more general cases. Adding a bunch of options,
like those of -renvars- or something similar, is not a big
deal. It's designing what comes before the comma which is
the key detail.
The implementation I'll optimistically assign
to StataCorp, as this really should _not_ be an .ado. It
should be part of the executable. The existing syntax
(which I'll call Syntax 1) is
Syntax 1: . rename oldname newname
(and for compatibility we really must keep that) and
it could generalise to
Syntax 2: . rename oldname1 [oldname2 [oldname3 ... ]]
newname1 [newname2 [newname3 ... ]]
or
Syntax 2:. rename oldvarlist newvarlist
or to
Syntax 2': . rename oldname1 newname1 [oldname2 newname2
[ oldname3 newname3 ... ]]
Both of those collapse to the existing syntax.
So why didn't -renvars- do that? I've forgotten
the history, and probably Jeroen Weesie has too,
but in practice with lots of renaming it's easier
than it should be to lose track of where you are.
That's why we introduced \ as a separator, so
that you can go "old names this way", "new names
that way"
. renvars oldvarlist \ newvarlist
or even
. renvars \ newvarlist
But that "\" still sticks in the craw, stylistically,
bringing back distant memories of -for-. And "/",
which is allowed but undocumented, is no better for
this purpose.
Nevertheless, it seems to me that Syntax 2
(which is more compatible with wildcards and variable
name ranges) should be allowed in -rename-.
Also I suggest that
Syntax 3: . rename oldvarlist, new(varlist)
with a special case
. rename , new(varlist)
should be allowed. The latter often is very
convenient. You have inherited some mess (e.g.
from a spreadsheet); you can see the names in
front of you (say in the Variables Window or
through -describe- or -ds-); you just want to
clean up.
So here's my suggestion for a generalised -rename-,
for discussion.
Syntax 1: . rename oldname newname
Syntax 2 (syntax 1, generalised): . rename oldvarlist newvarlist
Syntax 3: . rename [oldvarlist] [, new(varlist) <renvars_options>]
The syntax is, naturally, more complicated, but users could
easily choose. Quite a few Stata commands are now written
up in terms of some basic syntax (beginners start here) and
more advanced syntax.
Nick
[email protected]
Gary Longton replied to Peter Lachenbruch
> > I have a data set that I got with some oddball names like PyrexIA or
> > CuTaneousDA, etc. and I'd like to rename everything so all
> characters were
> > lowercase. Is there an easy way to do this via a foreach
> loop and a simple
> > command, or do I have to
> > rename PyrexIA pyrexia
> > rename CuTaneousDA cutaneousda
> >
> > I looked at the lower function but that seems to operate on
> variables rather
> > than names.
>
> Richard Williams, Roger Newson, and Richard Goldstein
> suggested -renvars-, a
> single command solution which will do this in one fell swoop.
> But I think you were also on the right track with what Nick
> Cox might call a
> "first principles" approach, using -foreach- and the lower()
> function. You just
> need to ensure that lower() is looking at the string variable
> name as an
> argument, rather than at the variable itself, by enclosing in
> double quotes. Eg.
>
> foreach var of varlist _all {
> local newname = lower("`var'")
> if "`var'" ~= "`newname'" {
> rename `var' `newname'
> }
> }
>
> should do it.
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