R: An aggregate example

sum_per_ID.md

An aggregate example

(data1 <- data.frame(id=c(rep(1,3),rep(2,3)),num=1:6))

  id num
1  1   1
2  1   2
3  1   3
4  2   4
5  2   5
6  2   6

aggregate(data1$num,list(data1$id),sum)

  Group.1  x
1       1  6
2       2 15

Or

aggregate(data1$num ~ data1$id,FUN=sum)

  data1$id data1$num
1        1         6
2        2        15