Spreading a two column data frame with tidyr

Question

I have a data frame that looks like this:

  a b
1 x 8
2 x 6
3 y 3
4 y 4
5 z 5
6 z 6

and I want to turn it into this:

  x y          


        

Answer 1

You can do this with dcast and rowid from the data.table package as well:

dat <- dcast(setDT(df), rowid(a) ~ a, value.var = "b")[,a:=NULL]

which gives:

> dat
   x y z
1: 8 3 5
2: 6 4 6

---

Old solution:

# create a sequence number by group
setDT(df)[, r:=1:.N, by = a]
# reshape to wide format and remove the sequence variable
dat <- dcast(df, r ~ a, value.var = "b")[,r:=NULL]

which gives:

> dat
   x y z
1: 8 3 5
2: 6 4 6