Group by ID, each element of the new table is a vector

Question

I have a table like this

data.table(ID = c(1,2,3,4,5,6), 
         R = c(\"s\",\"s\",\"n\",\"n\",\"s\",\"s\"), 
         S = c(\"a\",\"a\",\"a\",\"b\",\"b\",         


        

Answer 1

You can use dcast from reshape2 with the appropriate aggregating function:

library(functional)
library(reshape2)

dcast(df, R~S, value.var='ID', fun.aggregate=Curry(paste0, collapse=','))
#  R   a   b
#1 n   3   4
#2 s 1,2 5,6

Or even short as @akrun underlined:

dcast(df, R~S, value.var='ID', toString)