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Re: st: modifying egen to add a replace feature


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: modifying egen to add a replace feature
Date   Thu, 19 Jul 2012 09:09:01 +0100

Not so. Writing a new -egen- function so that it takes a -replace-
option is not the issue here. -egen- will throw out the call if -y- is
an existing variable before the function code is even entered. The
issue is cloning -egen- to do the replacement.

As I've signalled elsewhere, I think  it is easiest just to -drop-
what you don't want and/or do a -replace- afterwards.

Nick

On Thu, Jul 19, 2012 at 8:13 AM, Maarten Buis <maartenlbuis@gmail.com> wrote:
> On Wed, Jul 18, 2012 at 5:00 PM, Pradipto Banerjee wrote:
>> Is it possible to rewrite or modify egen, or create an ado file, such that I can simply write like this:
>>
>> bysort x: egen y = myfunc (y, a, b, ...), replace
>
> Yes, the logic behind the way -egen- works is that if you type -egen y
> = myfunc()-, -egen- will look for a file _gmyfunc.ado, which
> implements the function myfunc() and it also passes the option you
> have specified to that .ado file. So you can write your own -egen-
> functions. The easiest way to get started is to look at an existing
> similar function and addept that, e.g. look at -viewsource _gmean.ado.
>
>
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