How do I take the mean of the same element across multiple lists?-CodePudding

I have many lists contained within a larger list. I want to take the mean of the same entry in each of the lists.

Since I have many lists (100 plus) I want to be able to take the mean of all these lists by using 1:100 like I would for vector entries.

Here is some example, non working code.

## Make two lists
list_1 <- list()
list_1[[1]] <- 2


list_2 <- list()
list_2[[1]] <- 4

##Make a larger list to put the lists in
big_list <- list()

## Add lists to a larger list
big_list[[1]] <- list_1
big_list[[2]] <- list_2

## This doesn't work
mean(big_list[[1]][1], big_list[[2]][1], na.rm=TRUE)

## This does not work, but it is what I want
mean(big_list[[1:2]][1])

CodePudding user response：

You can use getElement inside sapply to pick out a vector comprising the first (or any specified) element from each sub-list:

sapply(big_list, getElement, 1)
#> [1] 2 4

and therefore

mean(sapply(big_list, getElement, 1))
#> [1] 3

CodePudding user response：

We could combine flatten from purrr package with unlist:

library(purrr)

  
x <- unlist(flatten(big_list))
x      
mean(x, na.rm = TRUE)

[1] 3

CodePudding user response：

This approach will do it as well:

sapply(1:length(big_list[[1]]), function(i) mean(sapply(big_list, function(x) x[[i]]), na.rm = TRUE))