On May 25, 2011, at 3:25 PM, Seth W Bigelow wrote:
I have a list that is made of lists of varying length. I wish to
create a
new vector that contains the last element of each list. So far I
have used
sapply to determine the length of each list, but I'm stymied at the
part
where I index the list to make a new vector containing only the last
item
of each list
mylist = list(c(1,2,3),c("cat","dog"),c("x","y","z","zz")) #
Create
list
last <- sapply(mylist,length) # Make vector with list lengths
last_only <- mylist[[1:length(mylist)]][last] # Crash and burn
trying to
make new vector with last items!
If you wanted to apply the successive values of last using "[" to
successive values of mylist there is a list-ish method via mapply:
> mapply("[", mylist, last)
[1] "3" "dog" "zz"
`mapply` is also the function underlying `Vectorise`
--
David Winsemius, MD
West Hartford, CT
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