can we iterate over two lists with purrr (not simultaneously)?

Question

Consider that I have a function f(x,y) that takes two argument and two lists

• x_var = list('x','y','z')
• and y_var = list('a','b')

Is there a purrr function that allows me to iterate every combination of one element in x_var and one element in y_var? That is, doing f(x,a), f(x,b), f(y,a), f(y,b) etc.

The usual solution would be to write a loop, but I wonder if there is more concise here (possibly with purrr.

Thanks!

Answer 1

You can nest your calls to map

library(purrr)
map(x_var, function(x) {
  map(y_var, paste, x)
})
[[1]]

[[1]][[1]]
[1] "a x"

[[1]][[2]]
[1] "b x"


[[2]]
[[2]][[1]]
[1] "a y"

[[2]][[2]]
[1] "b y"


[[3]]
[[3]][[1]]
[1] "a z"

[[3]][[2]]
[1] "b z"