How to sort a list of lists in R?

Question

I am attempting to sort a list of lists in R. Each sublist contains an integer and a character string. My goal is to order the lists such that the final list is sorted by the integers in ascending order. Below is an example of what I am trying to accomplish:

a <- list(-5,"help")
b <- list(3, "stack")
c <- list(1, "me")
d <- list(10, "overflow")

list.of.lists <- list(a,b,c,d)
magic.sort(list.of.lists)
# Below is not exactly how it would be displayed, but should be understandable
-5, "help"
1, "me"
3, "stack"
10, "overflow"

Is there a nice way within R to achieve this result? Ideally the result should be returned as a list of lists as well.

Answer 1

Try this:

list.of.lists[order(sapply(list.of.lists,'[[',1))]

Answer 2

You have a lot of structure in your list.of.lists. Depending on other processing you need to do, you might want to make it into a two-dimensional list like so:

list.2d <- sapply(list.of.lists, cbind)

and, possibly, from there, into a data frame like this:

df <- data.frame(t(list.2d))

(Technically, a data frame is a type of list.) Sorting by a particular set of columns, and extracting subsets of elements can then be a bit more conventional. (Though I also really like the accepted answer here.)