R help - Mar 2010 - how to make this sequence: 1,2,3,4,5,4,3,2,1

I'm just beginning R, with book Using R for Introductory Statistics, and one
of the early questions has me baffled.  The question is, create the
sequence: 1,2,3,4,5,4,3,2,1 using seq() and rep().

Now, as a programmer, I am punching myself to not be able to figure it out..
I mean, as simple as a for loop, but using seq, I am stumped.  I would think
c(1:5, 4:1) would be the brute force method with very non intelligent
coding..  there has to be a way to make the "turning point" (in this
case 5)
parametric right?  So you could change it later and the sequence will
reflect it.
-- 
View this message in context:
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Sent from the R help mailing list archive at Nabble.com.

c(x <- 1:5, rev(x[-length(x)]))



On 5 March 2010 07:04, kensuguro <magronbass at gmail.com>
wrote:
>
> I'm just beginning R, with book Using R for Introductory Statistics,
and one
> of the early questions has me baffled. ?The question is, create the
> sequence: 1,2,3,4,5,4,3,2,1 using seq() and rep().
>
> Now, as a programmer, I am punching myself to not be able to figure it
out..
> I mean, as simple as a for loop, but using seq, I am stumped. ?I would
think
> c(1:5, 4:1) would be the brute force method with very non intelligent
> coding.. ?there has to be a way to make the "turning point" (in
this case 5)
> parametric right? ?So you could change it later and the sequence will
> reflect it.
> --
> View this message in context:
http://n4.nabble.com/how-to-make-this-sequence-1-2-3-4-5-4-3-2-1-tp1579245p1579245.html
> Sent from the R help mailing list archive at Nabble.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.
>


-- 
____________________

Baptiste Augui?

Departamento de Qu?mica F?sica,
Universidade de Vigo,
Campus Universitario, 36310, Vigo, Spain

tel: +34 9868 18617
http://webs.uvigo.es/coloides

On 05-Mar-10 06:04:51, kensuguro wrote:
> 
> I'm just beginning R, with book Using R for Introductory Statistics,
> and one of the early questions has me baffled.  The question is,
> create the sequence: 1,2,3,4,5,4,3,2,1 using seq() and rep().
> 
> Now, as a programmer, I am punching myself to not be able to figure
> it out..
> I mean, as simple as a for loop, but using seq, I am stumped.
> I would think c(1:5, 4:1) would be the brute force method with very
> non intelligent coding..  there has to be a way to make the "turning
> point" (in this case 5) parametric right?  So you could change it
> later and the sequence will reflect it.
> -- 
> View this message in context:
> http://n4.nabble.com/how-to-make-this-sequence-1-2-3-4-5-4-3-2-1-tp15792
> 45p1579245.html
> Sent from the R help mailing list archive at Nabble.com.
You can indeed do it using seq(), and with rep() plus a little
help from something else:

seq():
  c(seq(1,5,1),seq(4,1,-1))

rep():
  cumsum(c(rep(1,5),rep(-1,4)))

Parametrised "1,2,...,n,(n-1),...,2,1":

  updown1 <- function(n){ c(seq(1,n,1),seq((n-1),1,-1)) }

  updown2 <- function(n){ cumsum(c(rep(1,n),rep(-1,(n-1)))) }

  updown1(10)
  # [1]  1  2  3  4  5  6  7  8  9 10  9  8  7  6  5  4  3  2  1
  updown2(10)
  # [1]  1  2  3  4  5  6  7  8  9 10  9  8  7  6  5  4  3  2  1

Ted.

--------------------------------------------------------------------
E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 05-Mar-10                                       Time: 08:14:53
------------------------------ XFMail ------------------------------

try this:

5 - abs(-4:4)


I hope it helps.

Best,
Dimitris


On 3/5/2010 7:04 AM, kensuguro wrote:
>
> I'm just beginning R, with book Using R for Introductory Statistics,
and one
> of the early questions has me baffled.  The question is, create the
> sequence: 1,2,3,4,5,4,3,2,1 using seq() and rep().
>
> Now, as a programmer, I am punching myself to not be able to figure it
out..
> I mean, as simple as a for loop, but using seq, I am stumped.  I would
think
> c(1:5, 4:1) would be the brute force method with very non intelligent
> coding..  there has to be a way to make the "turning point" (in
this case 5)
> parametric right?  So you could change it later and the sequence will
> reflect it.
-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014