[R] Merging data

[Chuck Cleland]

Brian Perron wrote:
> Hello all,
> 
> I am fairly new to R and am trying to bring together data from multiple sources.  Here is one problem that I cannot seem to crack – I hope somebody can help.  Let me simplify the problem:  Let’s say I have two datasets:  DATA1 and DATA2.  I would like to work with all the cases in DATA2.  I have additional variables on these cases in DATA1, which is a larger data set with many additional cases.  I know how to merge data sets if the datasets contain the same cases.  However, I want to eliminate all the cases from DATA1 that are not present in DATA2 and then merge.  The CASEID is my matching variable, and there are no duplicate variable names. 
> Any guidance would be greatly appreciated. 

Take closer look at the all.x and all.y arguments in ?merge.  Does this 
give what you want?

merge(DATA1, DATA2, by="CASEID", all.x=FALSE, all.y=TRUE)

-- 
Chuck Cleland, Ph.D.
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