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Re: st: How to quickly merge by the range of a third variable?


From   Taavi Lai <taavi.lai@ut.ee>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: How to quickly merge by the range of a third variable?
Date   Mon, 10 Oct 2005 14:46:45 +0300

Maybe there is a better way to do it but I would generate one dataset containing all the B-s and correstponding year by -append- and did the -merge- using this composite file by variables id and year. sth like

use b1, clear
gen year==1900
save b_comp, replace
use b2, clear
gen year==1901
append using b_comp
save b_comp, replace
use a, clear
merge year id using b_comp

And you could use looping for the first part but as I'm not proficent with it so I'd better leave it for other list members

Best regards
Taavi

Sean wrote:


Dear Statalisters,

I have a quick question about how to speed up the merging process.
Suppose I have one A dataset and several B dataset, denoted as B1, B2, B3, etc.

In A dataset, I have individuals' id numbers along with his/her birth
city and birth year. Now in B's datasets, it stores the information of
all the cities in a particular year, such as B1: all the cities for
year 1, B2: all the cities for year2, B3 for year3, etc. For example,
in year 1, I can get every city's population size for that year.

Now my goal is to get each individual's birth city population size, of
course, for that particular year when the individual was born. To
summarize, in dataset A, I have the following variables:

id birthyear birthcity

in B's datasets, I have

cityid population

I am aware that I should merge the right B dataset with A through
city, however, which year when the individual was born determines
which B dataset I should merge for that observation. I didn't find by:
or if... conditional command for "merge", as I imagined.

Is there a quickest way to finish this mission?

Thanks all.

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