[R] comparing the previous and next entry of a vector to a criterium

Kingsford Jones kingsfordjones at gmail.com
Mon Jan 26 00:21:02 CET 2009


How about:

a <- c(1,2,3,3,2,1,6,3,2)
b <- c(NA,a[-length(a)])
c <- c(a[-1],NA)
a[b==1 & c==3]
[1] 2 6


hth,

Kingsford Jones


On Sun, Jan 25, 2009 at 3:02 PM, Jörg Groß <joerg at licht-malerei.de> wrote:
> Hi,
>
> I have a quit abstract problem, hope someone can help me here.
>
> I have a vector like this:
>
>
>  x <- c(1,2,3,4,5,2,6)
>  x
>
> [1] 1 2 3 4 5 2 6
>
> now I want to get the number where the previous number is 1 and the next
> number is 3
> (that is the 2 at the second place)
>
> I tried something with tail(x, -1) ...
> with that, I can check  the next number, but how can I check the previous
> number?
>
> ______________________________________________
> 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.
>




More information about the R-help mailing list