st: AW: Problem looping over spells for an individual

["Martin Weiss" <martin.weiss1@gmx.de>]

<> 

Are you sure the line 

************* 
if `touse' {
*************

does what you want it to? -set trace on- or indeed use the recently
announced -ssc d tr-  and report what happens...


HTH
Martin


-----Ursprüngliche Nachricht-----
Von: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Im Auftrag von Ilona Carneiro
Gesendet: Mittwoch, 25. Februar 2009 17:24
An: statalist@hsphsun2.harvard.edu
Betreff: st: Problem looping over spells for an individual

Hello all

I am trying to write a programme that will run a command sequentially  
for observations of an individual. For each individual I have multiple  
spells and multiple failures. However, the twist is that I also need  
to exclude a period of time at risk after each treatment (prophylaxis)  
and after each failure (to prevent double-counting of failures that  
may actually be the same episode). I managed to do this without any  
problem for the treatment, but if an episode is disqualified (by a  
prior treatment or episode) I don't want it to disqualify a subsequent  
episode. Therefore I need to run the code sequentially for each spell  
of an individual, but using the marksample touse code to run it "by"  
individual doesn't seem to be working - the "forvalues" seems to  
always interpret _N as the last observation in the whole dataset, not  
the last observation for each individual.

I have the following code:

		program define byid, byable(recall, noheader)
		marksample touse
		sort `id' `start'
		if `touse' {
		forvalues i = 1(1)`=_N' {
		replace lagend = (`end' + `lag') if ((`tx' > 0 & `tx' < .) |
(`case'  
 > 0 & `case' < .))
		drop if lagend[`i'-1]>`end' & `id'[`i'-1]==`id'
		}
		}
		end
		
		gen lagend=. 	
		qui by id: byid

but I get the error:
2nd by group not found
r(111);

And the programme isn't doing what I need it to.

Any ideas?

Ilona

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