R: getting list of matching data frame values

Question

Two data sets:

people <- read.table(text="
pid
1
2
3
4
", header=TRUE)

comps <- read.table(text="
pid comp rank
1   1    0
1   3    1
1   2    2
2   4    0
2   1    1
2   3    2
3   1    0
3   2    1
3   4    2
", header=TRUE)

Trying to get a data frame of each unique pid with a list of their comparisons, like:

pid comps
1   1,3,2
2   4,1,3
3   1,2,4

Can't quite get there..

`data[,.(value=paste(value,collapse="")),by=group]` – Soheil May 21 '15 at 23:39 — Soheil, May 21 '15 at 23:39

score 0 · Answer 1 · answered May 21 '15 at 23:59

0

You can do this with aggregate:

aggregate(comp~pid, comps, paste, collapse=",")
#   pid  comp
# 1   1 1,3,2
# 2   2 4,1,3
# 3   3 1,2,4

answered May 21 '15 at 23:59

josliber

43,000
12
95
132

Excellent. Is there a way to add a third column? – Wells May 22 '15 at 00:10
@Wells sure, just return a vector, e.g. `aggregate(comp~pid, comps, function(x) c(paste(x, collapse=","), "A"))` – josliber May 22 '15 at 02:11

R: getting list of matching data frame values

1 Answers1