[R] jump in sequence

[Robin Hankin]

 > f <- function(n){as.vector(sweep(matrix(4:6,nrow=3,ncol=n),2,seq 
(from=0,by=9,len=n),"+"))}
 > f(10)
[1]  4  5  6 13 14 15 22 23 24 31 32 33 40 41 42 49 50 51 58 59 60 67  
68 69 76 77 78 85 86 87
 >

HTH

rksh


On 30 Jan 2007, at 14:29, Adrian DUSA wrote:

> Dear list,
>
> This should be a simple one, I just cannot see it.
> I need to generate a sequence of the form:
> 4  5  6 13 14 15 22 23 24
>
> That is: starting with 4, make a 3 numbers sequence, jump 6, then  
> another 3
> and so on.
> I can create a whole vector with:
> myvec <- rep(rep(c(F, T, F), rep(3, 3)), 3)
>
> Then see which are TRUE:
> which(myvec)
> [1]  4  5  6 13 14 15 22 23 24
>
>
> I'd like to avoid creating the whole vector if possible; for very  
> large ones
> it can be time consuming. There should be a way to only create the  
> proper
> indexes...
>
> Thanks for any hint,
> Adrian
>
> -- 
> Adrian Dusa
> Romanian Social Data Archive
> 1, Schitu Magureanu Bd
> 050025 Bucharest sector 5
> Romania
> Tel./Fax: +40 21 3126618 \
>           +40 21 3120210 / int.101
>
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--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
  tel  023-8059-7743