R help - Sep 2009 - a sequence that wraps around

I'd like to have something like seq() where I can pass in a length of the
desired sequence and a right limit so that the sequence goes up to the limit and
then starts again from 1.

# works now
seq(from=2, length.out=3)
[1] 2 3 4

# what I want
seq(from=2, length.out=3, rlimit=3)
[1] 2 3 1

# additional examples of what I want
seq(from=2, length.out=4, rlimit=3)
[1] 2 3 1 2
seq(from=2, length.out=4, rlimit=4)
[1] 2 3 4 1
seq(from=2, length.out=3, rlimit=2)
[1] 2 1 2

I can write this procedurally, but it seems like there ought to be a cleaner R
way of doing it. Thanks in advance for any suggestions.

Try rep:

rep(2:4, lenght.out = 3, times = 10)

On Wed, Sep 16, 2009 at 11:08 AM, Jack Tanner <ihok at hotmail.com>
wrote:
> I'd like to have something like seq() where I can pass in a length of
the
> desired sequence and a right limit so that the sequence goes up to the
limit and
> then starts again from 1.
>
> # works now
> seq(from=2, length.out=3)
> [1] 2 3 4
>
> # what I want
> seq(from=2, length.out=3, rlimit=3)
> [1] 2 3 1
>
> # additional examples of what I want
> seq(from=2, length.out=4, rlimit=3)
> [1] 2 3 1 2
> seq(from=2, length.out=4, rlimit=4)
> [1] 2 3 4 1
> seq(from=2, length.out=3, rlimit=2)
> [1] 2 1 2
>
> I can write this procedurally, but it seems like there ought to be a
cleaner R
> way of doing it. Thanks in advance for any suggestions.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O

On 2009.09.16. 16:08, Jack Tanner wrote:
> I'd like to have something like seq() where I can pass in a length of
the
> desired sequence and a right limit so that the sequence goes up to the
limit and
> then starts again from 1.
>
Disclaimer: total R beginner here (started to learn a 1 day ago), who 
just came to this list to learn.

You could use the modulo operator.
> # works now
> seq(from=2, length.out=3)
> [1] 2 3 4
>
> # what I want
> seq(from=2, length.out=3, rlimit=3)
> [1] 2 3 1
>
> # additional examples of what I want
> seq(from=2, length.out=4, rlimit=3)
> [1] 2 3 1 2
seq(from=1, length.out=4) %% 3 + 1
> seq(from=2, length.out=4, rlimit=4)
> [1] 2 3 4 1
seq(from=1, length.out=4) %% 4 + 1
> seq(from=2, length.out=3, rlimit=2)
> [1] 2 1 2
seq(from=1, length.out=3) %% 2 + 1

(the 'from' needed to be decreased by one, otherwise it'd start from
0)
>
> I can write this procedurally, but it seems like there ought to be a
cleaner R
> way of doing it. Thanks in advance for any suggestions.
>

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Jack Tanner
> Sent: Wednesday, September 16, 2009 7:08 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] a sequence that wraps around
> 
> I'd like to have something like seq() where I can pass in a 
> length of the
> desired sequence and a right limit so that the sequence goes 
> up to the limit and
> then starts again from 1.
> 
> # works now
> seq(from=2, length.out=3)
> [1] 2 3 4
> 
> # what I want
> seq(from=2, length.out=3, rlimit=3)
> [1] 2 3 1
> 
> # additional examples of what I want
> seq(from=2, length.out=4, rlimit=3)
> [1] 2 3 1 2
> seq(from=2, length.out=4, rlimit=4)
> [1] 2 3 4 1
> seq(from=2, length.out=3, rlimit=2)
> [1] 2 1 2
> 
> I can write this procedurally, but it seems like there ought 
> to be a cleaner R
> way of doing it. Thanks in advance for any suggestions.
The remainder (modulus) operator, x%%n, wraps to the range 0..n-1
but you can write a function that wraps to 1..n as
   mod1 <- function(x, n) (x-1L)%%n + 1L
Then pass the output of seq through that:
   > mod1(-2:10, 3)
    [1] 1 2 3 1 2 3 1 2 3 1 2 3 1

Bill Dunlap
TIBCO Software Inc - Spotfire Division
wdunlap tibco.com  
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

On 9/16/2009 10:08 AM, Jack Tanner wrote:
> I'd like to have something like seq() where I can pass in a length of
the
> desired sequence and a right limit so that the sequence goes up to the
limit and
> then starts again from 1.
> 
> # works now
> seq(from=2, length.out=3)
> [1] 2 3 4
> 
> # what I want
> seq(from=2, length.out=3, rlimit=3)
> [1] 2 3 1
> 
> # additional examples of what I want
> seq(from=2, length.out=4, rlimit=3)
> [1] 2 3 1 2
> seq(from=2, length.out=4, rlimit=4)
> [1] 2 3 4 1
> seq(from=2, length.out=3, rlimit=2)
> [1] 2 1 2
> 
> I can write this procedurally, but it seems like there ought to be a
cleaner R
> way of doing it. Thanks in advance for any suggestions.
Here's a start.  You probably want some sanity checks on the arguments; 
e.g. from=1 doesn't work because of the old 1:0 infelicity.

seq2 <- function(from, length.out, rlimit)
   rep(1:rlimit, length.out=length.out+from-1)[-(1:(from-1))]

Duncan Murdoch