I wrote: I found myself wishing for a function to rotate a vector. Is there one? I know about ?lag, but help.search("rotate") didn't find anything to the point.
Here I was regarding a vector as a _sequence_. The (one-step) rotation of c(u,v,w,x,y,z) is c(v,w,x,y,z,u). This is pretty much the way APL uses the word "rotate" (the vertical-bar-overstruck-with-a-circle operator).
Do you want:
c(x[-1],x[1]) for a one-step 'rotation'?
You could write a function:
function(x,n){
c(x[-(1:n)],x[1:n])
}> rotVec(1:10,5) [1] 6 7 8 9 10 1 2 3 4 5
except this fails for n=0 or n>length(x). Ah.
function(x,n){
n <- 1+(n-1)%%length(x)
c(x[-(1:n)],x[1:n])}
}seems to work. Even for negative n:
> rotVec(1:10,-1) [1] 10 1 2 3 4 5 6 7 8 9
Baz
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