[R] Merge data frame and keep unmatched

[Matthew Dowle]

Or if you need it to be fast,  try data.table.   X[Y] is a join when X and Y 
are both data.tables. X[Y] is a left join, Y[X] is a right join. 'nomatch' 
controls the inner/outer join i.e. what happens for unmatched rows.   This 
is much faster than merge().

"Gabor Grothendieck" <ggrothendieck at gmail.com> wrote in message 
news:971536df0906100704q433f5f99ld3f9c23e69d9529c at mail.gmail.com...
Try:

merge(completedf, partdf, all.x = TRUE)

or

library(sqldf) # see http://sqldf.googlecode.com
sqldf("select * from completedf left join partdf using(beta, alpha)")


On Wed, Jun 10, 2009 at 9:56 AM, Etienne B. Racine<etiennebr at gmail.com> 
wrote:
>
> 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
> --
> View this message in context: 
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> Sent from the R help mailing list archive at Nabble.com.
>
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