Look at the source code.
if (!is.null(length.out)) {
by <- (to - from)/(length.out[1] - 1)
}
If present, say length.out = 5
, it sets by
to be (to - from) / 4
. As for the latter,
if (!missing(along.with)) {
length.out <- length(along.with)
}
it allows you to, e.g., pass a list of length n
and then length.out
will be n
. I won't speak as to the usefulness of these arguments but I guess the author must have thought they'd come in handy.