R help - Mar 2012 - Maximum of remaining elements of vector

Dear community

I have the following problem. I'd like to have the maximum of the remaining
elements of a vector.

ex.
x<-c(1,2,3,4,1,2,3,1,2,1) 

f(x) =  c(4,4,4,4,3,3,3,2,2,1)

where the first element is: max(x[1:length(x])
the second one: max(x[2:length(x)])
the third one: max(x[3:length(x)]) and so on

Of course this can be done with a loop, but isn't there a nicer and faster
way to do so?

Regards,
bahave14

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> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of behave14
> Sent: Monday, March 12, 2012 11:15 AM
> To: r-help at r-project.org
> Subject: [R] Maximum of remaining elements of vector
> 
> Dear community
> 
> I have the following problem. I'd like to have the maximum of the
> remaining
> elements of a vector.
> 
> ex.
> x<-c(1,2,3,4,1,2,3,1,2,1)
> 
> f(x) =  c(4,4,4,4,3,3,3,2,2,1)
> 
> where the first element is: max(x[1:length(x])
> the second one: max(x[2:length(x)])
> the third one: max(x[3:length(x)]) and so on
> 
> Of course this can be done with a loop, but isn't there a nicer and
> faster
> way to do so?

f <- function(x) sapply(1:length(x), function(y) max(x[y:length(x)]))
f(x)
> 
> Regards,
> bahave14
> 
> --
> View this message in context: http://r.789695.n4.nabble.com/Maximum-of-
> remaining-elements-of-vector-tp4466499p4466499.html
> Sent from the R help mailing list archive at Nabble.com.
> 
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

----------------------------------------------
David L Carlson
Associate Professor of Anthropology
Texas A&M University
College Station, TX 77843-4352

On Mon, Mar 12, 2012 at 09:14:43AM -0700, behave14
wrote:
> Dear community
> 
> I have the following problem. I'd like to have the maximum of the
remaining
> elements of a vector.
> 
> ex.
> x<-c(1,2,3,4,1,2,3,1,2,1) 
> 
> f(x) =  c(4,4,4,4,3,3,3,2,2,1)
> 
> where the first element is: max(x[1:length(x])
> the second one: max(x[2:length(x)])
> the third one: max(x[3:length(x)]) and so on
Hi.

Try this.

  rev(cummax(rev(x)))

  [1] 4 4 4 4 3 3 3 2 2 1

Hope this helps.

Petr Savicky.