[email protected]
>
> I wrote,
>
> > Abbreviations can hurt you even if you don't ever use them,
> > such as
> >
> > i) dropping a variable you never intended to drop; or
> >
> > ii) inadvertently modifying the wrong variable
> >
> > For e.g., at some point in time your data contains
> > variables _foo_ and _foobar_. You no longer need _foo_
> > so you -drop- it. Later, (wrongly) believing _foo_ is
> > still defined, you -replace foo = ...- but it modifies
> > -foobar- instead since Stata finds no ambiguity in the
> > string literal _foo_. You might never notice this blunder.
> > Dealing with large datasets at times, with hundred of
> > variables possessing names that differ by only a character
> > or two, this can have unfortunate consequences. I almost
> > never use abbreviations myself either and typically, when
> > I want to modify _foo_, it is _foo_ I want to change and
> > certainly *not* _foobar_.
>
> to which Nick replied,
>
> > As mentioned in an earlier posting, safe dropping is
> > entirely controllable. The question came up on the list a
> few years
> > ago and I posted some code, although my guess was then
> > -- perhaps wrongly -- that it was a one-off request.
> >
> >(code omitted, see Nick's earlier email)
>
> Very true, and a similar routine can be used to handle safe
> replacing, i.e.
>
> cap prog drop safereplace
> program def safereplace
> *! in the spirit of safedrop.ado by N.J.Cox
> *! version 1.0 12fev2003 PJoly
> version 7.0
>
> unab V : `1'
> if "`V'" != "`1'" {
> di as err "`1' incomplete variable name"
> exit 198
> }
> replace `0'
> end
This is safer than -replace-, but note first that
it misinterprets e.g.
. safereplace mpg=weight
as `1' will be "mpg=weight". That's fixable, as
in
program def safereplace
*! 1.0.1 12 Feb 2003 NJC
*! version 1.0 12fev2003 PJoly
version 7.0
gettoken v rest : 0, parse("=")
unab V : `v'
if "`V'" != "`v'" {
di as err "`v' incomplete variable name"
exit 198
}
replace `0'
end
but two issues remain, at least: checking that
the expression in
= exp
does not use unabbreviated varnames and that
any -if- expression does not either.
>
> That said, these wrapper routines are not really the answer
> since any other
> .ado command (whether user-written or official Stata) that
> drops or replaces
> variables does so using -drop- and not -safedrop-. Like
> Lee, I wouldn't go
> as far as picketing in front of Stata headquarters but
> perhaps I could say
> that a pragmatic module to toggle abbreviations on or off
> would probably
> help me sleep better at night. :)
>
Point taken. This illustrates broader comments about the
wider implications of any change, in that programs you use also
affect your data: it is more than a matter of your own direct
input in the Command window and/or .do files.
Nick
[email protected]
*
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