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Re: st: funny behaviour of _N


From   "Ashim Kapoor" <ashimkapoor@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: funny behaviour of _N
Date   Thu, 28 Aug 2008 13:18:05 +0530

Thank you. appreciate the tips.

On Thu, Aug 28, 2008 at 12:55 PM, Philip Ryan
<philip.ryan@adelaide.edu.au> wrote:
> Ashim
>
> Funny perhaps, but logical to Stata.
>
> In code fragment 2. below you are using the -in- qualifier.  -help in-
> explicitly states that -in- is followed by a range and gives allowable
> syntax for that range.
> _N is not allowable syntax. Essentially it is not a number; it is what Stata
> calls a system variable. But its content as a number can be exposed by
> evaluation "on the fly".  Try:
>
> replace a=b in `=_N'
>
> In code fragment 1. below you have forced the evaluation of the *expression*
> _N by using the "=".  The number represented by _N now resides in local
> macro num.  When num is subsequently expanded it presents to -in- as a
> syntactically correct range.
>
> Probably about now, or shortly thereafter, you should read the User's Guide
> and at least selected parts of the Data Management volume of the
> documentation.  It will repay the effort.
>
> Phil
>
>
>
>  At 03:53 PM 28/08/2008, you wrote:
>>
>> Hello everyone,
>>
>> Please compare the following 2 code snippets : -
>>
>> 1.
>>
>> local num=_N
>> replace a=b in `num'
>>
>> 2.
>>
>> replace a=b in _N
>>
>> Surprisingly only the 1st one works ! Could some one tell me why ?
>>
>> Thank you,
>> Ashim
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>
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