Masanja, suppose the master data set is called individual.dta and the using
set, family.dta. The merge will work if you make sure that there is only
one observation per family_id in your using data (family.dta). You may
delete duplicate observations on family_id and index as follows:
sort family_id index
by family_id index : keep if _n==1
by family_id: assert _n==1
save family
If Stata returns
assertion is false
r(9);
after the -by ...: assert ...- line, this means you have more than one value
of index per family_id and must decide which value to retain before
proceeding any further. If assert doesn't return any output, you may issue
u individual
sort family_id
merge family_id using family, nokeep
This will fetch your index variable and match it based solely on family_id.
(Option -nokeep- states that Stata is not to retain observations in the
using data for which no matching family_id is found in the master data, if
any).
Or you can use -mmerge- and issue:
u individual
mmerge family_id using family, type(n:1)
where the option type(n:1) states that the merge variable, family_id, does
not form a key in the master data set but does form a key in the using set.
To form a key, the data must contain a single observation per group of merge
variable(s).
Patrick Joly
[email protected]
[email protected]
-----Original Message-----
From: [email protected] [mailto:[email protected]]
Sent: July 23, 2002 9:44 AM
To: [email protected]
Subject: st: Merging problem
Dear statalister
I have 2 files one containing information at household level and another
one at individual level. I would like to have each individual to in a
household have a value of an index which is at household level. When merged
two files on perm_id, here is what I get. Some individual are missing the
value of the index. When I do it on family_id, it gives me un-anticipated
results. What is the trick here?
family_id perm_id index
1. BUA000001 BUA000001002 .
2. BUA000001 BUA000001003 .
3. BUA000001 BUA000001004 .
4. BUA000001 BUA000001005 .
5. BUA000001 BUA000001006 .
6. BUA000001 BUA000001007 6.163015
10. BUA000004 BUA000004002 .
11. BUA000004 BUA000004003 .
12. BUA000004 BUA000004004 8.866956
Sincerely
Masanja
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