Matrix of combinations of two vectors

Question

I have two vectors, say:

x <- c("b", "p", "t")
y <- c("a", "e", "i")

I want to get a Matrix of their possible combinations.

df <- cbind(b=c("ba", "be", "bi"), p=c("pa", "pe", "pi"), t=c("ta", "te", "ti"))
rownames(df) <- c("a", "e", "i")

I have seen Possible combinations of a matrix in R but it doesn't do the trick here.

Also I have tried CJ(x,y) with data.table, but still I would need further steps to manipulate the data.

Is there a more simple solution to this?

score 3 · Accepted Answer · answered Jul 08 '19 at 17:18

3

We can use outer

out <- outer(x, y, FUN = paste0)
dimnames(out) <- list(x, y)

answered Jul 08 '19 at 17:18

akrun

Works perfectly...why did I not know that function? – Iskandar The Pupsi Jul 08 '19 at 17:20

score 1 · Answer 2 · answered Jul 08 '19 at 17:47

1

We also may use expand.grid

matrix(Reduce(paste0, expand.grid(x, y)), 3)
#      [,1] [,2] [,3]
# [1,] "ba" "be" "bi"
# [2,] "pa" "pe" "pi"
# [3,] "ta" "te" "ti"

answered Jul 08 '19 at 17:47

jay.sf

Thx, yes I have used expand.grid, yet it I have to say the outer() is less cumbersome – Iskandar The Pupsi Jul 09 '19 at 07:39
@IskandarThePupsi Yes, `outer` is great, there's not just one way to do it. – jay.sf Jul 09 '19 at 18:58

2 Answers2