How to attach values of each group?

Question

I want to attach the values of a group together, here is the sample:

data<-data.table(group=c("g1","g1","g2","g2","g1"),value=c(1,2,3,4,5))

my desired output would be:

     group  value
1:    g1     125
2:    g2     34

Values could be treated as numbers or characters.

Thanks!, I looked for . in the package, what exactly it does? — Soheil, May 21 '15 at 23:45
It can be used to substitute for `list(value=...)` - just saves a couple of characters. — thelatemail, May 21 '15 at 23:45
I suggest starting with the new HTML vignettes [here](https://github.com/Rdatatable/data.table/wiki/Getting-started). — Arun, May 22 '15 at 00:02

score 1 · Answer 1 · answered May 22 '15 at 02:46

In addition to the data.table solution from thelatemail, you can do this in base R:

aggregate(value ~ group, data, FUN = function(x) paste(x, collapse = ""))

Or with dplyr:

data %>%
  group_by(group) %>%
  summarise(value = paste(value, collapse = ""))

1 Answers1