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st: Teething troubles in using -gen, mod()-


From   "Clive Nicholas" <Clive.Nicholas@newcastle.ac.uk>
To   statalist@hsphsun2.harvard.edu
Subject   st: Teething troubles in using -gen, mod()-
Date   Wed, 2 Feb 2005 08:00:08 -0000 (GMT)

All,

Hiya! I'm attempting to create an -expand-ed dataset by creating a copy of
every observation (-id-) for each category of a multinomial variable
(-gewin-). There are five categories in total.

The data was already carefully checked and -sort-ed. After some very
careful reading of appropriate sources, I thought I'd cracked it with the
following:

. use mydata

. expand 5
(10496 observations created)

. gen alt = mod(_n, 5)

. sort id election alt

Thus, each duplicated observation within each quintet should take a unique
value of -alt-, from 0-4. Unfortunately, the new variable does not
-generate- as it should for the vast majority of groups:

. list id pano election name1997 gewin edyear alt in 1/30, sepby(id)

     +--------------------------------------------------------+
     | id   pano   election   name1997   gewin   edyear   alt |
     |--------------------------------------------------------|
  1. |  1      1          1   Aberavon       2     1976     0 |
  2. |  1      1          1   Aberavon       2     1976     1 |
  3. |  1      1          1   Aberavon       2     1976     1 |
  4. |  1      1          1   Aberavon       2     1976     2 |
  5. |  1      1          1   Aberavon       2     1976     3 |
     |--------------------------------------------------------|
  6. |  2      1          2   Aberavon       2     1983     0 |
  7. |  2      1          2   Aberavon       2     1983     1 |
  8. |  2      1          2   Aberavon       2     1983     2 |
  9. |  2      1          2   Aberavon       2     1983     2 |
 10. |  2      1          2   Aberavon       2     1983     4 |
     |--------------------------------------------------------|
 11. |  3      1          3   Aberavon       2     1984     0 |
 12. |  3      1          3   Aberavon       2     1984     1 |
 13. |  3      1          3   Aberavon       2     1984     3 |
 14. |  3      1          3   Aberavon       2     1984     3 |
 15. |  3      1          3   Aberavon       2     1984     4 |
     |--------------------------------------------------------|
 16. |  4      1          3   Aberavon       2     1987     0 |
 17. |  4      1          3   Aberavon       2     1987     2 |
 18. |  4      1          3   Aberavon       2     1987     3 |
 19. |  4      1          3   Aberavon       2     1987     4 |
 20. |  4      1          3   Aberavon       2     1987     4 |
     |--------------------------------------------------------|
 21. |  5      1          3   Aberavon       2     1986     0 |
 22. |  5      1          3   Aberavon       2     1986     1 |
 23. |  5      1          3   Aberavon       2     1986     2 |
 24. |  5      1          3   Aberavon       2     1986     3 |
 25. |  5      1          3   Aberavon       2     1986     4 |
     |--------------------------------------------------------|
 26. |  6      1          4   Aberavon       2     1988     0 |
 27. |  6      1          4   Aberavon       2     1988     1 |
 28. |  6      1          4   Aberavon       2     1988     1 |
 29. |  6      1          4   Aberavon       2     1988     2 |
 30. |  6      1          4   Aberavon       2     1988     3 |
     +--------------------------------------------------------+

If I'm missing something obvious here, it's very esoteric.

CLIVE NICHOLAS        |t: 0(044)7903 397793
Politics              |e: clive.nicholas@ncl.ac.uk
Newcastle University  |http://www.ncl.ac.uk/geps

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