<>
Also see http://www.stata-journal.com/sjpdf.html?articlenum=dm0019
HTH
Martin
-----Ursprüngliche Nachricht-----
Von: [email protected]
[mailto:[email protected]] Im Auftrag von Martin Weiss
Gesendet: Dienstag, 11. August 2009 13:58
An: [email protected]
Betreff: st: AW: unstable results with repeating the nearmrg command
<>
Could this possibly have anything to do with the -stable- option for -sort-?
HTH
Martin
-----Ursprüngliche Nachricht-----
Von: [email protected]
[mailto:[email protected]] Im Auftrag von John Hund
Gesendet: Montag, 10. August 2009 23:02
An: [email protected]
Betreff: st: unstable results with repeating the nearmrg command
I am having a very perplexing problem with the nearmrg command...it
seems to give different results on subsequent runs with the same
data. In addition, my co-author and I get different results on the
the same datasets, similarly sorted. An example of the problem is
below, using a very small (5 observation) dataset. The two datasets
are ageinfo1 and ageinfo2:
ageinfo1
+----------------------------+
| id gender age income |
|----------------------------|
1. | 4 1 12 56 |
2. | 3 1 25 21 |
3. | 1 1 34 23 |
4. | 5 2 18 75 |
5. | 2 2 40 43 |
+----------------------------+
Note that ageinfo1 is sorted by gender and age, and doesn't contain
any duplicate values.
ageinfo2
+-----------------------------+
| id gender income age |
|-----------------------------|
1. | 415 1 12 12 |
2. | 314 1 32 25 |
3. | 516 2 65 18 |
4. | 213 2 32 40 |
5. | 12 2 12 34 |
+-----------------------------+
Not necessary to be sorted, but I subsequently sort this file to
facilitate replication. Then issuing the following commands in order
gives:
. use ageinfo2
. sort gender age
. nearmrg gender using ageinfo1, nearvar(age) lower genmatch(newage)
. list
+-----------------------------------------------+
| id gender income age _merge newage |
|-----------------------------------------------|
1. | 415 1 12 12 3 12 |
2. | 314 1 32 25 3 25 |
3. | 516 2 65 18 3 18 |
4. | 12 2 12 34 3 18 |
5. | 213 2 32 40 3 40 |
+-----------------------------------------------+
. clear
. use ageinfo2
. sort gender age
. nearmrg gender using ageinfo1, nearvar(age) lower genmatch(newage)
. list
+-----------------------------------------------+
| id gender income age _merge newage |
|-----------------------------------------------|
1. | 415 1 12 12 3 12 |
2. | 314 1 32 25 3 12 |
3. | 516 2 65 18 3 18 |
4. | 12 2 12 34 3 18 |
5. | 213 2 32 40 3 40 |
+-----------------------------------------------+
. clear
. use ageinfo2
. sort gender age
. nearmrg gender using ageinfo1, nearvar(age) lower genmatch(newage)
. list
+-----------------------------------------------+
| id gender income age _merge newage |
|-----------------------------------------------|
1. | 314 1 32 25 3 25 |
2. | 415 1 12 12 1 . |
3. | 516 2 65 18 3 18 |
4. | 12 2 12 34 3 18 |
5. | 213 2 32 40 3 40 |
+-----------------------------------------------+
The first outcome is correct, but subsequent runs give different (and
incorrect) answers. My only guess at this point is that there is
something going on with a temporary file which is not being cleared,
but I don't know how that could happen. Has anyone else noticed a
problem with this?
Thanks in advance,
John
=================================
John Hund
Visiting Assistant Professor
Jones Graduate School of Business
Rice University
Houston, TX 77005
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