Re: st: generating duration-variable with multi-line spells

[n j cox <n.j.cox@durham.ac.uk>]

bysort id _spell (_seq) : gen duration = end[_N] - start[1] + 1

n j cox wrote:

> Jeph Herrin gave good answers to this. In addition,
> note that -tsspell- from SSC purports to be a general tool in
> this area. You would need to -tsset- the data first, but
> that can be done via a pseudo-time variable:
>
> bysort id (start) : gen t = _n
> tsset id t
>
> Then your spells are defined by -state- remaining
> constant:
>
> tsspell state
>
> at which various variables -- _spell _seq _end -- spring
> into being. Now your durations are just
>
> bysort id _spell (_seq) : gen duration = end[_N] - start[_N] + 1
>
> Now that's just re-inventing Jeph's logic, I imagine, but the help
> file has several small examples for other problems, so that -tsspell- 
> may help you in other ways.
>
> Nick
> n.j.cox@durham.ac.uk
>
>
> Henrik Lindegaard Andersen asked
>
> I want to generate a variable that counts the duration in some state. My 
> data looks like this:
>
> id  start   end     state   next_state
> 1   1       60      1       2
> 1   61      72      2       3
> 1   73      204     3       .
> 2   1       60      2       1
> 2   61      65      1       1
> 2   66      67      1       1
> 2   68      69      1       3
> 2   70      204     3       .
>
> If the state does not change (as for id 2 from 61 to 69) I want the new
> variable to be missing for all but one line. Therefore
>
> gen duration = end - start + 1 if state != next_state
>
> works from some of the spells. But what will work for the spells that 
> are split over several lines?
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