Group by multiple columns and sum other multiple columns

Question

I have a data frame with about 200 columns, out of them I want to group the table by first 10 or so which are factors and sum the rest of the columns.

I have list of

Answer 1

Using plyr::ddply:

library(plyr)
ddply(dtfr, .(name1, name2, namex), numcolwise(sum))