For Loop operating with last and first entry of array

If i have an array like this:

A=[1;5;6;8];

and i apply a simple for loop like this:

for k=1:4
    B(k)=A(k)+A(k+1);
end

How can i write the code, so the last entry of my array A makes the operation with the first entry aswell, namely 8+1=9?

Answer 1

[David Fletcher]

Like this?

A=[1;5;6;8];
B=A(1:length(A))+[A(2:length(A));A(1)]

B =

     6
    11
    14
     9

[Manuel Fuelling]

My problem is different than the example i gave:

Coeff is a 4x4 Matrix

    for m=1:3 
        syms x y z
            eqns = [Coeff(m,1)*x+Coeff(m,2)*y+Coeff(m,3)*z+Coeff(m,4) == 0, Coeff(m+1,1)*x+Coeff(m+1,2)*y+Coeff(m+1,3)*z+Coeff(m+1,4) == 0];
            vars = [x y z];
            [solX, solY, solZ] = solve(eqns, vars);
            arbpt_sym=[solX;solY;solZ];             
            arbpt_one_point=(double(arbpt_sym));    %mache sie als double
            arbpt(:,m) = arbpt_one_point;

    end

the last iteration should operate with the last row and first row of Coeff

[David Fletcher]

So you want it to operate as in the previous example but summing successive rows of a 2D matrix (and the last and first row) rather than the columns of the 1D matrix that you presented as your example?

Like this:

A=[1 1 1 1;2 2 2 2;3 3 3 3;4 4 4 4]

B=A(1:size(A),:)+[A(2:size(A),:);A(1,:)]

A =

     1     1     1     1
     2     2     2     2
     3     3     3     3
     4     4     4     4

B =

     3     3     3     3
     5     5     5     5
     7     7     7     7
     5     5     5     5