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st: RE: carrying observations forward if criteria met


From   Nick Cox <n.j.cox@durham.ac.uk>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   st: RE: carrying observations forward if criteria met
Date   Thu, 2 Feb 2012 21:00:11 +0000

David Kantor keeps an eye on the list and can speak for his -carryforward- (SSC). 

(As always, please explain where user-written programs you refer to come from.) 

However, as you say your problem concerns a wide not long data structure, so I think needs to be solved in a different way. 

Focusing on S1 as an example, it seems that just you need a loop something like 

forval j = 2/8 { 
	local k = `j' - 1 
	replace S1_week`j' = S1_week`k' if inrange(S1_week`k', 3, .) 
} 

Applying the same rule to other symptoms would then be two nested loops. 

However, I am queasy about supporting your changing your data, which someone might regret, so advise that you do this on a clone of your data, or equivalently keep a copy of the original variables somewhere.  

Also, I have not tested this code, so you should only try it out on a copy of your data. 

There was a general review of working "row-wise" in 

SJ-9-1  pr0046  . . . . . . . . . . . . . . . . . . .  Speaking Stata: Rowwise
        (help rowsort, rowranks if installed) . . . . . . . . . . .  N. J. Cox
        Q1/09   SJ 9(1):137--157
        shows how to exploit functions, egen functions, and Mata
        for working rowwise; rowsort and rowranks are introduced

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

laura hendrix

I have a set of time-series data where patients complete a weekly
survey with items describing the severity of 14 symptoms (scoring
1-lowest to 5-highest) for 8 weeks with.  It is in wide format, ie

idno   S1_week1   S2_week1  S3_week1....S1_week2  S2_week2  S3_week3....etc

1            3                 2              1    ........     1
          2               3
2            1                 1              2   .........     1
         3               4
3
4
etc

a score of >=3 is considered clinically relevant.  I would like to be
able to read across the weeks for each symptom, and as soon as a score
of 3 or higher is encountered in the 8 week period, the rest of the
values for the period are replaced with this value.  for example, if a
patient has a score of 3 in week 2, then the scores for that symptom
will be replaced with 3 for weeks 3,4,5,6,7, and 8.  If there is a
higher score in later weeks, it will be overwritten by the first
clinically relevant score.

This is similar to the "carryforward" ado file but I believe that only
replaces missing values?

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