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

[Jörg Groß]

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?