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

[Taavi Lai <taavi.lai@ut.ee>]

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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