Extract Names of Objects from List

Extract names of objects from list

Making a small tweak to the inside function and using lapply on an index instead of the actual list itself gets this doing what you want

x <- c("yes", "no", "maybe", "no", "no", "yes")
y <- c("red", "blue", "green", "green", "orange")
list.xy <- list(x=x, y=y)

WORD.C <- function(WORDS){
  require(wordcloud)

  L2 <- lapply(WORDS, function(x) as.data.frame(table(x), stringsAsFactors = FALSE))

  # Takes a dataframe and the text you want to display
  FUN <- function(X, text){
    windows() 
    wordcloud(X[, 1], X[, 2], min.freq=1)
    mtext(text, 3, padj=-4.5, col="red")  #what I'm trying that isn't working
  }

  # Now creates the sequence 1,...,length(L2)
  # Loops over that and then create an anonymous function
  # to send in the information you want to use.
  lapply(seq_along(L2), function(i){FUN(L2[[i]], names(L2)[i])})

  # Since you asked about loops
  # you could use i in seq_along(L2) 
  # instead of 1:length(L2) if you wanted to
  #for(i in 1:length(L2)){
  #  FUN(L2[[i]], names(L2)[i])
  #}
}

WORD.C(list.xy)

Extract names of dataframes in a list passed to a function in R

purrr::imap comes in handy in this type of case where we need to iterate over the list of elements (or atomic vectors) and their names parallelly:

purrr::imap(list.ts, plot_func)

where
plot_func <- function(df, name) plot(df, ylab="", xlab="Months", col="red", main = name)

R extract name of object within purrr::map()

We can use imap (which calls map2 to pass the names index) instead of map and extract the list names with .y and the values with .x. Here imap is calling map2

library(purrr)
imap(input, ~ .y)
#$df1
#[1] "df1"

#$df2
#[1] "df2"

Or instead of .x, .y, can also use ..1 and ..2

imap(input, ~ ..2)

Basically imap is calling map2

 imap
  function (.x, .f, ...) 
 {
.f <- as_mapper(.f, ...)
map2(.x, vec_index(.x), .f, ...)
  }

---

If we want to use map, option is to loop over the names or the sequence of list

map(names(input), ~ .x)

and for subsetting the values, use the [[

map(names(input), ~ input[[.x]])

---

With map, the .x is only the values of the data and the names of the list are not passed into it

---

If we want to use base R, then an option is Map

Map(function(u, v) v, input, names(input))

or using lapply

lapply(names(input), function(nm) nm)

R get objects' names from the list of objects

You can write your own list() function so it behaves like data.frame(), i.e., uses the un-evaluated arg names as entry names:

List <- function(...) {
  names <- as.list(substitute(list(...)))[-1L]
  setNames(list(...), names)
}

my.list <- List(model.product, model.i, model.add)

Then you can just access the names via:

names(my.list)

R: How to access the name of an element of a list?

Rephrasing the question, the goal is to create a list where the list elements have names according to the objects that have been assigned to them. If a is assigned to the first list element, the first name should automatically become a.

This can be achieved by using makeNamedList instead of list. The function makeNamedList is a condensed result from this question.

makeNamedList <- function(...) {
  structure(list(...), names = as.list(substitute(list(...)))[-1L])
}

Example:

mylist <- makeNamedList(cars, iris)
str(mylist)

# List of 2
# $ cars:'data.frame':  50 obs. of  2 variables:
#   ..$ speed: num [1:50] 4 4 7 7 8 9 10 10 10 11 ...
# ..$ dist : num [1:50] 2 10 4 22 16 10 18 26 34 17 ...
# $ iris:'data.frame':  150 obs. of  5 variables:
#   ..$ Sepal.Length: num [1:150] 5.1 4.9 4.7 4.6 5 5.4 4.6 5 4.4 4.9 ...
# ..$ Sepal.Width : num [1:150] 3.5 3 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 ...
# ..$ Petal.Length: num [1:150] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 ...
# ..$ Petal.Width : num [1:150] 0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 ...
# ..$ Species     : Factor w/ 3 levels "setosa","versicolor",..: 1 1 1 1 1 1 1 1 1 1 ...

So makeNamedList(cars, iris) is equivalent to list(cars = cars, iris = iris).

Extract names of second [given] level of nested list in R

A possible solution, based on purrr::map_depth:

library(tidyverse)

map_depth(x, 1, names) %>% unlist(use.names = F)

#> [1] "one_1" "one_2" "one_3" "two_1" "two_2"

How to get the name of each element of a list using lapply()?

Here's a solution using purrr. It seems to run faster than the solution by aaronwolden but slower than akrun's solution (if that's important):

library(purrr)
map2(test, names(test), function(vec, name) {
    names(vec) <- c("index", "type", name)
    return(vec)
})

$a
     [,1] [,2] [,3]
[1,]    1    1    1
attr(,"names")
[1] "index" "type"  "a"    

$b
     [,1] [,2] [,3]
[1,]    2    2    2
attr(,"names")
[1] "index" "type"  "b"    

Extract names of these objects and add to new array in React Native?

You can use the map function. If your original array is:

const array = [
  { id: 4, name: "Banana" },
  { id: 5, name: "Watermelon" },
  { id: 3, name: "Pineapple" },
]

you can create a new array by doing the following:

const namesArray = array.map((item) => item.name)

namesArray is:

["Banana", "Watermelon", "Pineapple"]

Extract items in a list using variable names in R

Instead of dat_raw$`12`[[31]], you can have dat_raw[[12]][[31]] if 12 is the 12th element of the JSON. So your for loop would be:

for (m in 1:12) {
     print(dat_raw[[m]][[31]])
}

---

Related Topics