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RE: st: Labeling different kinds of missing observations


From   Rituparna Basu <basur@pamfri.org>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Labeling different kinds of missing observations
Date   Fri, 20 Apr 2012 06:52:32 +0000

Hi Nick,

Thank you so much for the resources and the code. 
I did run the macro but it said 'invalid syntax'. 

I think I did not mention my question properly. I would like to transform the following data :
 ID  Y1  Y2  Y3  Y4  Y5  Y6  Y7
 1    .      .      x    x     x     x   x
 2    .     x      .    x     x     x   x
 3    .      .      x    x    .     x   x
 4    .      x     .    x     x     .   x
 5    x     x     .   x      x     x  .

Transform to:

ID  Y1  Y2  Y3  Y4  Y5  Y6  Y7
 1   0      0      x    x     x     x   x
 2    0     x      1    x     x     x   x
 3    0      0      x    x   1.     x   x
 4    0      x     1    x     x     1   x
 5    x     x     1   x      x     x  1

Basically, replace the missing of var Y* (missing obs before and after the first obs (as you can see)) and not create a new variable.
I apologize  for the confusion but any help is greatly appreciated!

Thank you!

Regards,
RB 

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
Sent: Thursday, April 19, 2012 12:15 PM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Labeling different kinds of missing observations

This sounds as if you want indicators

missbefore  1 if any missing before first non-missing and 0 otherwise

missafter     1 if any missing after etc.

Here's a sketch. Code not tested.

gen missbefore = 0
gen missafter = 0
gen first = .

qui forval J = 1/7 {
       replace missbefore = 1 if missing(Y`J') & `J' < `first'
       replace first = `J' if missing(first) & !missing(Y`J')
       replace missafter = 1 if missing(Y`J') & `J' > `first'
}

I think of these problems in this way.

1. I need to initialise an indicator. Sometimes the initial value does not matter; sometimes it does. You have to think it through for each problem.

2. I need to loop over the variables.

3. The first key then is "when do I change my mind?"

4. The second key is "if I change my mind, is the indicator then fixed, or may I need to update it?"

But why not -reshape long-?

See also

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

On Thu, Apr 19, 2012 at 7:10 PM, Rituparna Basu <basur@pamfri.org> wrote:

> I am trying to generate a variable that will indicate missing BEFORE FIRST YEAR of OBSERVATION and missing AFTER FIRST YEAR of OBSERVATION.
> Here is a sample of the data:
>
> ID  Y1  Y2  Y3  Y4  Y5  Y6  Y7
> 1    .      .      x    x     x     x   x
> 2    .     x      .    x     x     x   x
> 3    .      .      x    x    .     x   x
> 4    .      x     .    x     x     .   x
> 5    x     x     .   x      x     x  .
>

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