Thanks for the reference to the article, Nick; I didn't realize that it
was available for free, so I didn't go looking for it. (My library
doesn't subscribe to STB or SJ and, given the state budget situation, I
don't think that's going to change.)
As for the help being terse, that's for certain!
Michael
Nick Cox wrote:
> The help _is_ complete on this question, just terse.
>
> The affordability of the manuals remains a separate issue, although no
> doubt it bites hard. I can't add to many earlier comments on this issue.
> But there is no taboo on talking about this on the list. It's just the
> same question will get the same answers!
>
> One of the forms that
>
> expansion_optr
>
> can take is listed as
>
> = exp
>
> and links take you to other entries for Stata's language, including exp
> as indicating an expression.
>
> Michael also overlooked my point that a relevant tutorial exists with no
> marginal cost to him.
>
> Nick
> [email protected]
>
> Michael I. Lichter
>
> Thanks Nick and Martin, although I don't see this in either -help macro-
>
> or -help variables- ... unless it's the uninterpretable (to me)
>
> "[...] `expansion_optr' [...]"
>
> in -help macro- (FYI: Stata 9.2). I'm guessing that it IS in [P] Macro,
> but I frankly can't afford the manuals and wish Stata would make them
> available free online like SAS or on the install DVD like SPSS or at a
> reasonable price in PDF form online which I know is one of those things
> you're not supposed to talk about on Statalist. Grrr.
>
> Michael
>
> Nick Cox wrote:
>
>> I think what Michael wants to know is documented better at -help
> macro-.
>>
>> `=exp' where exp is an expression lets you evaluate an expression on
> the
>> fly and use its result.
>>
>> `=2 + 2' would be in these terms: the expression is 2 + 2; Stata would
>> evaluate that; and the command would see 4.
>>
>> As the example implies, the expression can be a single item such as
> _N.
>> This has been in Stata since (I think) sometime during Stata 7 but was
>> not documented until Stata 8. There is a discussion within
>>
>> SJ-3-2 pr0009 . . . . . . . . . . . . . Speaking Stata: Problems
> with
>> lists
>> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
> N.
>> J. Cox
>> Q2/03 SJ 3(2):185--202 (no
>> commands)
>> discusses ways of working through lists held in macros
>>
>> which is visible under the 3-year rule.
>
>
>> P.S. The help and the manuals are, as always, the first documentation
> to
>> think of. Typically, the FAQs fill in some odd gaps or fill out some
>> tricky topics.
>>
>> Martin Weiss
>>
>> see -help _variables-. The equal sign evaluates this -expression- so
> no
>> need
>> for any -macro-...
>>
>> Michael I. Lichter
>>
>>> Whoa! This works even though `=_N' is clearly not a macro. Is this an
>
>>> undocumented feature, or is it a "real" part of Stata that will stick
>
>>> around? I'm sorry if this is discussed somewhere in the FAQ -- I have
>> no
>>> idea how to search for it.
>> Philip Ryan wrote:
>>>> Try:
>>>>
>>>> forvalues i = 1/`=_N' {
>>>>
>>>> ....
>>>>
>>>> }
>>>>
>> *
>> * For searches and help try:
>> * http://www.stata.com/help.cgi?search
>> * http://www.stata.com/support/statalist/faq
>> * http://www.ats.ucla.edu/stat/stata/
>
--
Michael I. Lichter, Ph.D.
Research Assistant Professor & NRSA Fellow
UB Department of Family Medicine / Primary Care Research Institute
UB Clinical Center, 462 Grider Street, Buffalo, NY 14215
Office: CC 125 / Phone: 716-898-4751 / E-Mail: [email protected]
*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
