Find the first and last elements of all vectors in a list

c_topntail returns an 2xN matrix containing the start and end of each of the vectors in the input list. Length 0 vectors are ignored, while length 1 vectors are duplicated

For c_topntail_list, a list of the same length as L having the same elements when their length is <=2 or the first and last elements when length>2.

c_topntail(L)

c_topntail_list(L)

Arguments

L

a list containing integer vectors, typically a seglist

Value

For c_topntail an integer matrix. For c_topntail_list a list.