[R] Question about merge()

[Wensui Liu]

MERGE DATA FRAMES BY 2 OR MORE VARIABLES
#######################################
# MERGE 2 DATA FRAMES BASED ON        #
# 2 OR MORE VARIABLES                 #
#######################################

data1<-data.frame(x.id1 = 1:10, x.id2 = (1:10) * 2, x = rnorm(length(1:10)));
data2<-data.frame(y.id1 = seq(1, 20, by = 2), y.id2 = seq(1, 20, by =
2) * 2, y = rnorm(length(1:10)));

merged<-merge(data1, data2, by.x = c("x.id1", "x.id2"), by.y =
c("y.id1", "y.id2"), all = TRUE);


On 9/23/06, Jonathan Greenberg <jgreenberg at arc.nasa.gov> wrote:
> If I want to do a join based on *two* matching fields in two data frames,
> can merge() handle this?  It appears to only handle a single matching column
> -- do I need to make a "metacolumn" or is there some way to do this?  E.g.:
>
> Dataframe 1 contains columns A,B,C and Dataframe 2 contains A,B,D
>
> I want an output A,B,C,D which places C and D together if A and B match
> (otherwise, make two new rows, e.g. Ax,Bx,Cx,nodata and Ay,By,nodata,Dy)
>
> --j
>
> --
> Jonathan A. Greenberg, PhD
> NRC Research Associate
> NASA Ames Research Center
> MS 242-4
> Moffett Field, CA 94035-1000
> Office: 650-604-5896
> Cell: 415-794-5043
> AIM: jgrn307
> MSN: jgrn307 at hotmail.com
>
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>


-- 
WenSui Liu
(http://spaces.msn.com/statcompute/blog)
Senior Decision Support Analyst
Cincinnati Children Hospital Medical Center