Using purrr::pmap within mutate to create list-column

Question

I understand how to use map to iterate over arguments in a df and create a new list column.

For example,

params <- expand.grid(param_a = c(2, 4,          


        

Answer 1

You can do this:

df.preprocessed <- dplyr::as.tbl(params) %>%
  dplyr::mutate(test_var = purrr::pmap(list(x = param_a
                                            ,y = param_b
                                            ,z = param_c
                                            ,u = param_d),
                                              ~ rep(5,.x)*.y                                                
  )
  )

or

df.preprocessed <- dplyr::as.tbl(params) %>%
  dplyr::mutate(test_var = purrr::pmap(list(x = param_a
                                            ,y = param_b
                                            ,z = param_c
                                            ,u = param_d),
                                       ~ rep(5,..1)*..2                                       
  )
  )

The second way is more general as you can use ..3, ..4 etc...