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RE: st: RE: Creating missing data


From   celdjt@umich.edu
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: RE: Creating missing data
Date   Wed, 03 Nov 2004 22:08:56 -0500

Thanks for the help on this but the procedure does not quite do it. Or, more precisely, it overdoes it. That is, instead of replacing with a missing value only the entry time for the first record for every fifth multiple-record case, it replaces all entry times with missing values for all records in every fifth multiple-record case. I am aiming to replace only the first entry time value in the first record for every fifth multiple-record case.

--On Thursday, November 04, 2004 1:45 AM +0000 Nick Cox <n.j.cox@durham.ac.uk> wrote:


Correct. I guess the -egen- should just select those cases.

. bysort whateverisyourid : gen multiple = _N > 1
. egen id = group(whateverisyourid) if multiple
. bysort id (entrytime):
         replace somevar = . if _n == 1 & mod(id,5) == 0

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

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Keith Dear
Sent: 04 November 2004 01:36
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: RE: Creating missing data


But celdjt said he wanted to do this for every fifth
*multiple-record*
case. He could first drop the single-record cases, apply
Nick's code, then
append them back. Or is there a neater way?
kd

At 12:18 PM 4/11/04, you wrote:
> Suppose your identifiers run 1, 2, ... . If this isn't true,
>
> . egen id = group(whateverisyourid)
>
> will make it so.
>
> Now, if I understand you correctly, you want to
>
> . bysort id (entrytime):
>         replace somevar = . if _n == 1 & mod(id,5) == 0
>
> Nick
> n.j.cox@durham.ac.uk
>
> celdjt@umich.edu
>
> > My
> > question is about making an adjustment to the surrogate
data set. The
> > surrogate data set contains about 3500 cases, some of which
> > have just one
> > record per case, and others have multiple records. Each
record has a
> > variable recording an entering time and an exit time for
that record.
> > Hence, single record cases have one entry time and one exit
> > time; multiple
> > record cases have multiple entry and multiple exit times. I
> > would like to
> > convert the first entry time for every fifth multiple-record
> > case in this
> > data set into a missing value. Are there any suggestions for
> > how this might be done.
>
> *
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> *   http://www.stata.com/support/statalist/faq
> *   http://www.ats.ucla.edu/stat/stata/


==========================================================
Dr Keith B.G. Dear
Senior Fellow
* Centre for Mental Health Research (CMHR)
* National Centre for Epidemiology and Popn Health (NCEPH)

The Australian National University
Canberra ACT 0200 Australia
T: +61 2 6125 4865 (NCEPH)
T: +61 2 6125 8439 (CMHR)
F: +61 2 6125 0740

CRICOS Provider #00120C
http://nceph.anu.edu.au/Staff_Students/staff_pages/dear.php

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