[R] Merge data frame and keep unmatched

Etienne B. Racine etiennebr at gmail.com
Wed Jun 10 15:56:16 CEST 2009


Hi,

With two data sets, one complete and another one partial, I would like to
merge them and keep the unmatched lines. The problem is that merge() dosen't
keep the unmatched lines. Is there another function that I could use to
merge the data frames.

Example:

completedf <- expand.grid(alpha=letters[1:3],beta=1:3)
partdf <- data.frame(
	alpha= c('a','a','c'),
	beta = c(1,3,2),
	val = c(2,6,4))

mergedf <- merge(x=completedf, y=partdf, by=c('alpha','beta'))
# it only kept the common rows
nrow(mergedf)

Thanks, 
Etienne
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