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Re: st: RE: identifying spells in panel data


From   Morten Vejs Willert <amklinik@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: identifying spells in panel data
Date   Fri, 25 Sep 2009 07:45:52 +0200

Dear Nick Cox

Point taken regarding the spelling of Cox regression - and thank you
for your thorough reply. I will try to follow your suggestions, and
have this morning obtained a copy "Speaking Stata - Identifying
spells", which I am sure wil guide me further along in the right
direction.

Greetings... Morten

2009/9/24 Nick Cox <n.j.cox@durham.ac.uk>:
> On behalf of all Coxes everywhere, especially numero uno Sir David, I'd
> like to request the spelling Cox regression.
>
> Note that -spell- (SSC) is superseded by -tsspell- (SSC), but neither is
> not applicable to wide format data anyway.
>
> In this case, you can just concatenate your data into one string and
> look for spells using -strpos()-.
>
> egen wall = concat(w1-w48)
>
> gen workspell = strpos(wall, "0000")
>
> This will return the start week of the first such spell if there is one
> and 0 otherwise.
>
> Hence
>
> gen byte success = workspell > 0
>
> In general, however, you'd be better off after a -reshape- to long.
>
> See also
>
> SJ-7-2  dm0029  . . . . . . . . . . . . . . Speaking Stata: Identifying
> spells
>        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N.
> J. Cox
>        Q2/07   SJ 7(2):249--265                                 (no
> commands)
>        shows how to handle spells with complete control over
>        spell specification
>
>
> Nick
> n.j.cox@durham.ac.uk
>
> Morten Vejs Willert
>
> In relation to performing a cox regression, I am looking for a way to
> identify spells in a dataset containing longitudinal panel data of 48
> week-by-week registrations on absenteeism from work.
>
> The dataset is in wide format. For each participant(=id) there are 48
> variables (one per week) containing either the value 0 (=working) or
> the value 1 (=absent from work). The week-by-week variables are named
> consecutively w1, w2, w3, ... w48, as illustrated below:
>
> id     w1     w2     w3     w4     w5     w6 ..... w48
> 1       1       1       1       0       0       0          0
> 2       1       0       0       0       0       0          0
> 3       1       1       1       1       1       0          0
> 4       0       0       0       0       0       0          0
> ...
> 102   1       1       1       1       0       0          0
>
>
> I am interested in determining when a participant has had a spell of
> four consecutive weeks working - so in my dataset I want to identify
> spells of 4 consecutive 0's, when combing through the variable w1 to
> w48 - and I want to generate two new variables: 'success' describing
> if the participant has had such a spell (values 0 or1), and
> 'successtime' denoting the first week of the identified spells (values
> 1 to 45).
>
> I have tried to use the command -spell- to achieve this, but with no
> success. Does anyone have a solution to this problem?
>
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>

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