How can I remove an element from a list?

Question

I have a list and I want to remove a single element from it. How can I do this?I've tried looking up what I think the obvious names for this function would be in the reference manual and I haven't found anything appropriate.

Answer 1

If you know the list's index value for the item then you can remove that item by subtracting that index value in a list slice, eg. if you want to remove the second element from mylist and reinitialize without that element, you could write

mylist <- mylist[-2]

There are other functions such as which() that can output the indices of elements of arrays that match some specified condition. You can then apply the above method using the stored indices from which() to remove those elements

eg. remove non-numeric elements:

mylist <- list(1,2,3,'nan')

indices <- which(is.na(as.numeric(mylist)))

mylist <- mylist[-indices]

What should be supplied as an argument to which() is problem dependent and beyond scope.

Alternatively, subset() can be used to directly manipulate the array.

mylist <- list(1,2,3,'nan')

subset(mylist, !is.na(as.numeric(mylist)))