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st: egen first/lastnm


From   Devra Golbe <dgolbe@gmail.com>
To   statalist <statalist@hsphsun2.harvard.edu>
Subject   st: egen first/lastnm
Date   Fri, 22 Feb 2008 14:58:22 -0500

-egen(newvar) = first(varname)-

(from the egenmore functions) produces missing values when I did not expect that behavior. newvar is missing for observations in which varname is missing. The same is true for -egen newvar = lastnm(varname)- Is that the behavior I should have expected? In contrast, -egen (newvar) = mean(varname) populates newvar even if varname is missing. See the example below my signature

Thanks,
Devra


------
Devra Golbe
Dept. of Economics
Hunter College



input n id x

n id x
1. 1 1 10
2. 2 1 9
3. 3 1 11
4. 4 2 12
5. 5 2 .
6. 6 2 11
7. 7 3 .
8. 8 3 .
9. 9 3 10
10. end

. egen y = first(x), by(id)
(3 missing values generated)

egen z = lastnm(x), by(id)
(3 missing values generated)

egen m=mean(x), by(id)

. list

+------------------------------+
| n id x y z m |
|------------------------------|
1. | 1 1 10 10 11 10 |
2. | 2 1 9 10 11 10 |
3. | 3 1 11 10 11 10 |
4. | 4 2 12 12 11 11.5 |
5. | 5 2 . . . 11.5 |
|------------------------------|
6. | 6 2 11 12 11 11.5 |
7. | 7 3 . . . 10 |
8. | 8 3 . . . 10 |
9. | 9 3 10 10 10 10 |
+------------------------------+


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