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

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

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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