Utilizing a vectors index number when using map-CodePudding

I have a function which utilizes purrr::map. I would like to access the index number of the vector element being used in the map function.

In the example below, I would like to add the index number to each value:

library(tidyverse)

c(2, 3) %>% 
  map_dbl(~.x   [index])

So, for example, for the first element, 2, the map function would evaluate and return:

2 1 = 3, where 1 = its index in the source vector

Whereas for the second element, 3, the map function would evaluate and return:

3 2 = 5, where 2 = its index in the source vector

CodePudding user response：

Instead of map, use imap, which returns the index with .y (if not named). It is mentioned in the documentation of ?imap

imap_xxx(x, ...), an indexed map, is short hand for map2(x, names(x), ...) if x has names, or map2(x, seq_along(x), ...) if it does not.

c(2, 3) %>% 
    imap_dbl(~ .x   .y )

-output

[1] 3 5

CodePudding user response：

Or:

library(tidyverse)

c(2, 3) %>% 
  map2_dbl(1:length(.), ~.x   .y)

#> [1] 3 5