On Apr 25, 2010, at 2:22 PM, Chuck Cleland wrote:
On 4/25/2010 2:10 PM, Alan Lue wrote:
Hi,
Is there a way to specify the last element of a vector, similar to
"end" in
MATLAB?
v[end]
would be MATLAB for
v(length(v))
in R.
While `v(length(v))' does yield the last element, that approach
fails in the
following,
rep(v, each=2)[-c(1,length(v))]
Cleland's example works, but I thought you might be interested in
ideas about why your approach did not. The length of you rep-ed vector
was twice as long as the original so this method, which only adds a
factor of two to the length argument, succeeds:
> rep(v, each=2)[-c(1,2*length(v))]
[1] 1 2 2 3 3 4
--
David.
which is meant to duplicate all elements of `v' except for the
first and
last. (I.e., if `v <- 1:4', then we want '1 2 2 3 3 4'.)
v <- 1:4
rep(v, c(1, rep(2, length(v) - 2), 1))
[1] 1 2 2 3 3 4
So the question is, is there a better way specify the last element
of a
vector? If not, is there a better way to duplicate all elements of
a vector
except for the first and last? (I know you can achieve this using
two
lines, but I'm writing because I want to do it using one.)
Alan
--
Chuck Cleland, Ph.D.
NDRI, Inc. (www.ndri.org)
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New York, NY 10010
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