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RE: st: Multiple tests


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Multiple tests
Date   Fri, 4 Apr 2003 12:22:14 +0100

Ronnie Babigumira
> 
> When it comes to the test, you use
> 
> foreach s of local suff {
> 	if `i++' == 0 test avg`s' = delta`s'
> 	else test avg`s' = delta`s', accum
> }
> 
> While Ernest uses
> 
> foreach origvars of varlist spring crsgpa frstsem  {
>           if `i'==0 test avg`origvars' = avg`origvars'
>           else         test avg`origvars' = avg`origvars' , accum
>           local i = `i' + 1
> }
> 
> (ignoring what is in foreach and focusing on the actual 
> test) You have one
> line less (i am guessing it is achieved by if `i++'). 
> Please throw some more
> light on this.

Stata 8 adds, for local macros, the ++ and -- increment 
and decrement operators familiar to programmers in C 
and similar languages. 

In particular 

`i++' 

means -- in context -- use the current 
value `i' here and _then_ increment local macro i 
(bump it by by 1), so that any later reference 
to `i' will use the incremented value. 

`++i' increments the local macro i and then uses it. 

`i--' and `--i' are "use then decrement (bump down by 1)" and 
"decrement then use".  

See [U] 21.3.4 and [U] 21.3.7 or [P] macro. 

Nick
n.j.cox@durham.ac.uk

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