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Re: st: Double loop over unbalanced panel


From   WEBER Sylvain <sylvain.weber@unine.ch>
To   "<statalist@hsphsun2.harvard.edu>" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Double loop over unbalanced panel
Date   Sat, 3 Nov 2012 05:53:52 +0000

Hi. 
I think you don't need any loop. - by - can be used instead. 
Try 
bysort id (t): replace chc=(chc[_n-1]*ph+cont)/p if mi(chc)

Note that the - if mi(chc) - condition is very important. Otherwise, you would replace all values of chc; not only missing values. 

Best,

Sylvain

Le 2 nov. 2012 à 14:00, "Fernando Luco" <flucoestatalist@gmail.com> a écrit :

> Hi Nick,
> 
> The data and the formula look as follows
> 
> input id t str1 ch p str1 chh ph cont con_c chc
> 1 1 "a" 2 "" . 1 0.5 1 1
> 1 2 "b" 3 "a" 4 3 1 .
> 1 2 "b" 3 "a" 4 3 1 .
> 1 3 "a" 1 "b" 2 2 2 .
> 1 4 "c" 4 "a" 3 3 .75 .
> 1 5 "d" 2 "c" 5 1 .5 .
> 2 3 "d" 2 "" . 1 1 2
> 2 4 "a" 3 "d" 3 3 1 .
> 2 5 "b" 1 "a" 2 2 2 .
> 2 6 "a" 2 "b" 2 1 .5 .
> end
> 
> foreach k of numlist 1/2{
> foreach w of numlist 2/T_k{
> replace chc=(chc[`w'-1]*ph+cont)/p if _n==`w' & id==`k'
> }
> }
> 
> Thanks,
> 
> Fernando
> 
> On Fri, Nov 2, 2012 at 3:39 PM, Nick Cox <njcoxstata@gmail.com> wrote:
>> I think the best advice depends on what -formula()- is, which you
>> don't tell us.
>> 
>> That said
>> 
>> foreach of numlist ...
>> 
>> in both your examples can be recast more simply as -forval- loops.
>> 
>> Nick
>> 
>> On Fri, Nov 2, 2012 at 8:12 PM, Fernando Luco <flucoestatalist@gmail.com> wrote:
>>> Hi,
>>> 
>>> I have an unbalanced panel and I need to do a loop over individuals and
>>> observations. My data looks as follows (I have other variables that are not
>>> represented in this example)
>>> 
>>> id t  chc
>>> 1 1 .5
>>> 1 2 .
>>> 1 3 .
>>> 1 4 .
>>> 1 5 .
>>> 2 3 1
>>> 2 4 .
>>> 2 5 .
>>> 2 6 .
>>> 
>>> What I want to do is, for each individual (id) to complete the values in
>>> chc according to a formula that depends on other variables. However, the
>>> number of times that each individual appears differs across individuals. I
>>> would like to do something such as
>>> 
>>> foreach k of numlist 1/2 { /*the 2 has to be changed to the total number of
>>> individuals*/
>>> foreach w of numlist 2/T_k { /* where T_k corresponds to the number of
>>> times individual 2 appears*/
>>> replace chc=formula(`w')
>>> }
>>> }
>>> 
>>> I don't know how to define T_k in the correct way such that it varies
>>> across individuals (so 5 for individual 1 and 4 for individual 2).
>>> 
>>> Thanks,
>>> 
>>> Fernando
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