3

I have the following nasty, nested list

Edit: updated to include value_I_dont_want

mylist <- list(
  list(
    nested_1 = list(
      nested_2 = list(
        list( value_I_want = "a", value_I_dont_want = "f"),
        list( value_I_want = "b", value_I_dont_want = "g")
      )
    )
  ),
  list(
    nested_1 = list(
      nested_2 = list(
        list( value_I_want = "c", value_I_dont_want = "h"),
        list( value_I_want = "d", value_I_dont_want = "i"),
        list( value_I_want = "e", value_I_dont_want = "j")
      )
    )
  )
)

And I want to get all the value_I_wants

I know I can use the following code within a for loop 

mylist[[x]]$nested_1$nested_2[[y]]$value_I_want

But I want to improve my map skills. I understand how to use map_chr when the list is a single level but I haven't found many resources on plucking from very nested lists. I also know I can use [[ but haven't found good documentation for when this is appropriate?

Any help appreciated!

MayaGans
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1 Answers1

2

If we need the 'yay's

library(purrr)
library(dplyr)
map(mylist, ~ .x$nested_1$nested_2 %>% unlist%>% grep("^yay", ., value = TRUE))

Or use pluck to extract the elements based on the key 'value_I_want' after looping over the list with map

map(mylist, ~ .x$nested_1$nested_2 %>% 
                     map(pluck, "value_I_want") )
akrun
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  • Ah ha! Thank you! This is super helpful but what I didn't include in my minimal example is that there are other elements in the unnamed list `list( value_I_want = "yay_1", value_I_dont_want = "no"),` so I cant just use unlist. I will update my question to reflect that – MayaGans Mar 29 '20 at 17:41
  • Thank you again for your help - I'd like to avoid using grep because in my real data the values are actually quite different. Thanks for helping me to pinpoint my issue - so sorry for the confusion! – MayaGans Mar 29 '20 at 17:49
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    @MayaGans with `pluck` we are only getting those elements that have the key 'value_I_want' – akrun Mar 29 '20 at 17:50