I have the following list
n = 1:10 s = c("aa", "bb", "cc", "dd", "ee") b = c(TRUE, FALSE, TRUE, FALSE, FALSE) x = list(n, s, b, 3) For a vector v we can remove elements like this: v[-(1:2)]. But how do we go about removing elements from a list? Say that I want x where x[[1]] should now have the last two elements removed - is there an easy way to do this?
We can use head to remove the last two elements of the specific list element by using negative index and update the list
f1 <- function(lst, ind){ lst[[ind]] <- head(lst[[ind]], -2) lst } f1(x, 1) #[[1]] #[1] 1 2 3 4 5 6 7 8 #[[2]] #[1] "aa" "bb" "cc" "dd" "ee" #[[3]] #[1] TRUE FALSE TRUE FALSE FALSE #[[4]] #[1] 3 Or another option using replace in the comments by @Frank
f2 <- function(lst, ind) replace(lst, ind, list(head(lst[[ind]], -2))) 
list elements have the last 2 elements removed
x removed Try this C# (Just substitute your values): [Code] string[] array = new string[] { "1", "2", "3", "4", "5", "6", "7" }; List<string> list = new List<string>(array); //you can sort List<string>! list.Sort(); list.Remove("4");//remove specieifed item. list.RemoveAt(2);//remove item from index. list.RemoveRange(1, 2);//remove a range of items. [/Code] 
v[-(1:2)] removes the first and second elements. R is indexed starting from 1, not zero.Update: Avoid negative result values in the length calculation (many thanks @Frank)
To remove the last two elements of the first list item use:
x[[1]] <- x[[1]][seq_len(max(0, length(x[[1]]) - 2))] which results in
> x [[1]] [1] 1 2 3 4 5 6 7 8 [[2]] [1] "aa" "bb" "cc" "dd" "ee" [[3]] [1] TRUE FALSE TRUE FALSE FALSE [[4]] [1] 3 Note that the example v[-(1:2)] of the OP does NOT remove the last two elements but the first two:
> n[-(1:2)] [1] 3 4 5 6 7 8 9 10 If you were using names for the list items the code would even be more intuitive:
... x = list(n=n, s, b, 3) # name the first list item "n" ... x$n <- x$n[seq_len(max(0, length(x$n) - 2))] If the vector has less than two elements it is shortened to a length of zero.
