CODEWITHSUNDEEP
rlistpiperenamepurrr
Hi CLH
Hi CLH

Reputation: 49

Rename list elements which has names starting with specified characters using purrr package

I have a list with element names like x.height, x.weight, y.height, y.length, z.weight, z.price I would like to extract the elements which names start with "x." and rename these element by removing their prefix "x.". This can be done in two steps:

list.new <- list.old %>% keep(str_detect(names(.), "^x.")) 
names(list.new) <- str_replace(names(list.new), "x", "")

My first question: how to combine these two steps in a pipeline?

At the end, I would like to process the list for all of the different prefixes "y.", "z." to get a new list with the renamed sublists like:

List of 3
 $ x:List of 2
  ..$ height: num 100
  ..$ weight: num 200
 $ y:List of 2
  ..$ height: num 300
  ..$ length: num 400
 $ z:List of 2
  ..$ weight: num 500
  ..$ price: num 600

Is it possible to do this using a single pipeline?

Upvotes: 0

Views: 890

Answers (2)

Alexlok
Alexlok

Reputation: 3134

You can simply use setNames() or set_names():

list.old <- list(
  x.height=1, x.weight=2, y.height=3, y.length=4, z.weight=5, z.price=6
)

list.old %>%
  keep(startsWith(names(.), prefix)) %>%
  set_names(str_replace(names(.), prefix, ""))
# $height
# [1] 1
# 
# $weight
# [1] 2

And to apply to many prefixes, use the previous code as a function:

prefix_list <- c("x","y","z")

map(prefix_list,
    function(prefix) list.old %>%
      keep(startsWith(names(.), prefix)) %>%
      set_names(str_replace(names(.), prefix, ""))
) %>%
  set_names(prefix_list)
# $x
# $x$.height
# [1] 1
# 
# $x$.weight
# [1] 2
# 
# 
# $y
# $y$.height
# [1] 3
# 
# $y$.length
# [1] 4
# 
# 
# $z
# $z$.weight
# [1] 5
# 
# $z$.price
# [1] 6

Upvotes: 1

SavedByJESUS
SavedByJESUS

Reputation: 3334

You can achieve what you want the following way. Note that this requires that you have a recent version of the dplyr package (>= 1.0.0).

library(dplyr)
library(stringr)
library(purrr)

list.old <- list(
  x = list(x.height = 100, x.weight = 200),
  y = list(y.height = 300, y.length = 400),
  z = list(z.weight = 500, z.price = 600)
)

list.new <- list.old %>%
  map(as_tibble) %>%
  map(~ rename_with(.x, ~ str_remove(.x, "^[xyz]\\."))) %>%
  map(as.list)

str(list.new)

List of 3
 $ x:List of 2
  ..$ height: num 100
  ..$ weight: num 200
 $ y:List of 2
  ..$ height: num 300
  ..$ length: num 400
 $ z:List of 2
  ..$ weight: num 500
  ..$ price : num 600

Upvotes: 0

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