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


From   Jeph Herrin <[email protected]>
To   [email protected]
Subject   Re: st: generating duration-variable with multi-line spells
Date   Fri, 01 Dec 2006 08:08:16 -0500

Henrik,

I assume you do not want to combine observations with the
same -id- and -state-, which would simplify the problem.
So how about:

 gen newstart=start
 bys id (start): replace newstart=newstart[_n-1] if state==state[_n-1]
 bys id newstart: gen duration = end-newstart+1 if _n==_N

This produces:


  +-----------------------------------------------------------+
  | id   start   end   state   next_s~e   newstart   duration |
  |-----------------------------------------------------------|
  |  1       1    60       1          2          1         60 |
  |  1      61    72       2          3         61         12 |
  |  1      73   204       3          .         73        132 |
  |  2       1    60       2          1          1         60 |
  |  2      61    65       1          1         61          . |
  |  2      66    67       1          1         61          . |
  |  2      68    69       1          3         61          9 |
  |  2      70   204       3          .         70        135 |
  +-----------------------------------------------------------+


which I think is what you want.

hth,
Jeph


Henrik Lindegaard Andersen wrote:
Dear Statalisters,

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?



Regards

Henrik Lindegaard

Research Associate
AKF, Institute of Local Government Studies - Denmark
Nyropsgade 37, DK-1602 Copenhagen V
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