Combining large data sets with unique IDs

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Sgolenbro
Posts: 2
Joined: Tue Aug 09, 2016 6:31 pm

Combining large data sets with unique IDs

Postby Sgolenbro » Tue Aug 09, 2016 7:24 pm

So I've got a conundrum that I'm hoping someone else can take a crack at and show me up...

I have one large data set (n=500K, apx) w/ survey responses, all with unique respondent IDs.

Recently, we just received new variables from this same population (e.g. test scores, anthropometric data), in a new data set; but are under strict guidelines to analyze ONLY the original 500K participants. The problem is that the new data set (test/anthros) has about 4 million more rows, since it has both respondents not in our original data AND it has multiple rows for individuals that took the new test multiple times.

So I need to add the new variables to this original data set for those 500K, matching by nearest date, while leaving out the extras.

**Example**
If respondent ABC1001 took the original survey on 6/1/2014, and the new data set has 4 rows for ABC1001--once for each time he's taken the new tests in 2013, 2014, 2015, and 2016--I need to match his original survey responses with his 2014 test/anthro data. But I need to do this on a large scale by writing in some way to not only combine cases, but to combine the RIGHT cases by finding the smallest difference in dates...

I realize that's a little much for a forum--anyone have any tips though?? Anything AT ALL would be HUGELY appreciated, I'm happy to clear anything up if something's not clear too.

Thank you!

Sam

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