st: Re: Panel Differences

["Jake Kendall" <kendall_jake@hotmail.com>]

Hi Alex,

I would create a new variable that uniquely identifies each observation in 
turn, tsset by that, then 1st difference . Try:

gen unique = _n
tsset unique
gen d_interview=.
replace d_interview= D.interview if D.year ==0
replace d_interview = 365 - L.interview+interview if D.year !=0

*the first line just makes a variable that has the value of the observation 
number (must be sorted in the right way)
*the rest just fills in the differences accounting for the year change on 
the last observation in a given year
*you may have to set the first observation by hand as there is no 1st 
difference

others may have more elegant solutions...

Jake
----- Original Message ----- 
From: "Alexander Nervedi" <alexnerdy@hotmail.com>
To: <statalist@hsphsun2.harvard.edu>
Sent: Monday, May 01, 2006 11:19 AM
Subject: st: Panel Differences



> Hi,
>
> I have data on a panle of 10 kids for 10 years observed approximately 
> every 3 weeks. It kind of looks like as below.
>
> For each child I'd like to get the difference in the date of interviews. 
> Simple things like
>
> gen diff = interview - L1.interview fail me since the tsset command 
> assumes that the day preceeding the current interview date (i,t), is a (i, 
> t-1) where the t-1 is not specific to the i but for anyonein the data set. 
> Consequently interview(i, t-1) may well be missing.
>
> I was wondering what the simplest way would be to get the average distance 
> between interview dates for each of these 10 kids over the 10 year period.
>
> thanks.
>
> alex
>
>
> ID   year  interview
> 1      1      10
> 1      1      47
> ...
> 1      1    365
> 1      2      31
> 1      2      62
> ...
> 1      2    340
> ...
> 1     10    342
> 2      1     10
>
> ...
>
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