split.feat(x, f, drop=FALSE, start.from="left", pointer.only=FALSE,
...)featnrow.feat(x).nrow.feat(x)TRUE, return an object which is a pointer
to a features object stored in C (advanced use only).feat with the same features as x but
with all features of length > max.length broken into segments
(starting from the first position in feature). The last piece
of each split segment may be smaller than max.length