Re: st: Collapsing with strings

[Gary Longton <glongton@fhcrc.org>]

Yes, as usual, a cleaner and much more simple solution to Daphna's duplicates 
problem than mine, staircase or not!

- Gary

Nick Cox wrote:

> L'esprit de l'escalier:
>
> When observations come in blocks of 2 another
> approach is possible that removes the need for 
> sorting on each variable, although one prior
>
> sort id 
> is needed. 
> foreach var of varlist var1-var3 {
> 	by id: replace `var' = `var'[3 - _n] if missing(`var') 
> }
>
> When the missing values are in the first observation, _n 
> is 1 and 3 - _n is 2. When the second, _n is 2 and 3 - _n
> is 1. Hence 3 - _n indexes the other observation in blocks 
> of 2. This works regardless of variable type. 

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