Hello,
There are some alternatives without using sqldf or another package.
1.
tmp2 <- aggregate(item ~ id, data = df1, FUN = unique)
Then merge() like you've done.
2.
tmp3 <- merge(df1, df2)
tmp3[!duplicated(tmp3), ]
Hope this helps,
Rui Barradas
Em 08-05-2014 10:44, Massimo Bressan escreveu:
given this "bare bone" example:
df1 <- data.frame(id=rep(1:3,each=2), item=c(rep("A",2), rep("B",2),
rep("C",2)))
df2 <- data.frame(id=c(1,2,3), who=c("tizio","caio","sempronio"))
I need to group the first dataframe "df1" by "id" and then merge with
the second dataframe "df2" (again by "id")
so far I've manged to accomplish the task by something like the
following...
# start
require(sqldf)
tmp<-sqldf("select * from df1 group by id")
merge(tmp, df2)
#end
now I'm wonderng if there is a more efficient and/or elegant way to
perform it (also because in fact I'm dealing with much more "heavy"
dataframes);
may be possible through a single sql statement? or by using a different
package functions (e.g. dplyr)?
my attempts towards these alternative approaches miserably failed ...
thanks
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