How do I make a vector into a loop?

for example I need to make the last element (N) in my vector such that (N+1) will correspond to the first element in the vector?

[Azzi Abdelmalek]

Can you give a short example: if x=[1 2 3 4], what should be the result?

Answer 1

[Dan K]

I think I understand... Are you saying that if you have a five element vector A(1:5), then you want A(6) to actually reference A(1)?

One way I can see to do this is to create a custom index function as an anonymous function. This is a way of doing it for reading only.

>> A = 1:5
A =
     1     2     3     4     5

>> B = @(A,ind)A(mod(ind,length(A)))
B = 
    @(A,ind)A(mod(ind,length(A)))
>> B(A,2)
ans =
     2
>> B(A,7)
ans =
     2
>> B(A,8)
ans =
     3

Here's a quick way of doing it for writing:

    >> A = 1:5;
    >> realind = @(x)mod(x,length(A));
    >> A(realind(27))
    ans =
         2
    >> A(realind(27)) = 5
    A =
         1     5     3     4     5
    >>

[Matt Tearle]

Nice! Slight glitch, though: B(A,5) will barf. You need to tweak the mod calculation:

>> B = @(A,ind)A(1+mod(ind-1,length(A)))

[Laura]

Thanks this is what i meant and ive managed to do it now. Thanks again.