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stackoverflow.com › questions › 10776742 › how-can-i-make-a-list-of-lists-in-r

You can easily make lists of lists

list1 <- list(a = 2, b = 3)
list2 <- list(c = "a", d = "b")
mylist <- list(list1, list2)

mylist is now a list that contains two lists. To access list1 you can use mylist[[1]]. If you want to be able to something like mylist$list1 then you need to do somethingl like

mylist <- list(list1 = list1, list2 = list2)
# Now you can do the following
mylist$list1

Edit: To reply to your edit. Just use double bracket indexing

a <- list_all[[1]]
a[[1]]
#[1] 1
a[[2]]
#[1] 2

Answer from Dason on Stack Overflow

Stack Overflow

stackoverflow.com › questions › 10776742 › how-can-i-make-a-list-of-lists-in-r

How can I make a list of lists in R? - Stack Overflow

Top answer

1 of 5

72

You can easily make lists of lists

list1 <- list(a = 2, b = 3)
list2 <- list(c = "a", d = "b")
mylist <- list(list1, list2)

mylist is now a list that contains two lists. To access list1 you can use mylist[[1]]. If you want to be able to something like mylist$list1 then you need to do somethingl like

mylist <- list(list1 = list1, list2 = list2)
# Now you can do the following
mylist$list1

Edit: To reply to your edit. Just use double bracket indexing

a <- list_all[[1]]
a[[1]]
#[1] 1
a[[2]]
#[1] 2

2 of 5

11

Using your example::

list1 <- list()
list1[1] = 1
list1[2] = 2
list2 <- list()
list2[1] = 'a'
list2[2] = 'b'
list_all <- list(list1, list2)

Use '[[' to retrieve an element of a list:

b = list_all[[1]]
 b
[[1]]
[1] 1

[[2]]
[1] 2

class(b)
[1] "list"

Creating complex list structure from data frame in R

Creating an array or lists of lists in R

r - For loop to create lists

r - How to create a list of list and then perform a vectorised function over it

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Statology

statology.org › home › how to create a list of lists in r (with example)

How to Create a List of Lists in R (With Example)

July 11, 2022 - #define lists list1 <- list(a=5, b=3) list2 <- list(c='A', d='B') #create list of lists list_of_lists <- list(list1, list2) The following example shows how to use this syntax in practice. The following code shows how to create a list that contains 3 lists in R:

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If you have lists of lists of data frames, can you join into a single data frame? Or several? dplyr::bind_rows(my list[[1]]) for example More on reddit.com

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I tend to use the purrr package. The functions keep(), keep_at(), pluck() etc are extremely useful for these situations. If you have an example I (and others) can give you some specific tips. More on reddit.com

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Converting list of lists into data frame

library(jsonlite)

library(purrr)

library(data.table)

# This isn't strictly json - it's a file where each line is json

# Read data line by line

raw <- readLines("https://files.pushshift.io/reddit/comments/sample_data.json")

# Convert each line from json to a list

json_list <- map(raw, fromJSON)

# Convert each list to a data.table

dt_list <- map(json_list, as.data.table)

# Harness the power of rbind list

dt <- rbindlist(dt_list, fill = TRUE)

# Done

dt

# Here is the same thing in a single pipeline

dt2 <- readLines("https://files.pushshift.io/reddit/comments/sample_data.json") %>%

map(fromJSON) %>%

map(as.data.table) %>%

rbindlist(fill = TRUE)

# Happy to explain any steps - enjoy

Top answer

1 of 5

6

Try map_df, which will output your map result in data frame format. Maybe not applicable to your current dilemma but I have found it helpful. There are other map variants that might get what you need better than a list.

2 of 5

6

Map. Map within map. Usually don't go deeper than 3 levels. Flatten is useful. Pluck is handy. tibble::enframe followed by pivot_longer. I try to unnest innermost two levels by flattening them.

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reddit.com › r/rlanguage › handling lists of lists (of lists)

r/Rlanguage on Reddit: Handling lists of lists (of lists)

October 29, 2023 -

I often use map() in my code, which gives output in list format. My data can be in the form of a list of lists containing dataframes, so I'm often getting the results of my code functionals in the form of lists of lists of lists (of vectors).

I find these multi-lists hard to manipulate and also to present results clearly when they're in this form. Is the many-list hierarchy a common side-effect of working in R? What are your common strategies for working with layers of lists?

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2

If you have lists of lists of data frames, can you join into a single data frame? Or several? dplyr::bind_rows(my list[[1]]) for example

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October 28, 2024 -

Hello, I parsed a son file in R. Now I have an issue that cannot resolve as I have the issue of extracting this lists of lists of lists that also have different row numbers each list and also different columns as, depending on the object, some columns may not be there. How best access these dataframes buried into lists and also these columns hidden into dataframes nested into lists? I am really struggling. Thanks.

Top answer

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I tend to use the purrr package. The functions keep(), keep_at(), pluck() etc are extremely useful for these situations. If you have an example I (and others) can give you some specific tips.

2 of 5

2

Try to see if fleece::rectangularize ( renv::install("thieled/fleece") ) is able to turn your list of lists into a data.frame. That should make it easier to filter the contents. Otherwise, you can do that conversion to df yourself with tibble::enframe + repeated use of tidyr::unnest_wider and unnest_longer. If you want to keep the data as lists, you can use either purrr, rrapply, or data.tree to work your way through the list.

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