Only Shifting the outer loop

This is the assignment I was given: he script should assume an m-by-n array A (m, n >= 2) is assigned in the Command Window. The value mover should also be assigned. The script should rotate all of the values on the outer loop of the array by mover spots clockwise and call the output A_out.

Example executions follow:

>> A = [1 2 3 4 5; 6 7 8 9 10; 11 12 13 14 15; 16 17 18 19 20]; mover = 2;
>> script25 
A_out = 
  11     6     1     2     3 
  16          7           8          9           4
    17         12         13        14         5
    18         19         20        15        10

So far I have where it shifts by two positions but I don't know how to get the jut the outer loop to shift. Any hints?

A = [1 2 3 4 5; 6 7 8 9 10; 11 12 13 14 15; 16 17 18 19 20]
mover = 2
B = circshift(A,mover,2)

[Gina Barlage]

A = [1 2 3 4 5; 6 7 8 9 10; 11 12 13 14 15; 16 17 18 19 20]; mover = 2;

A_out = zeros(size(A)); outerIndices = [A(1,:), A(2:end-1,end).', A(end,end:-1:1),A(end-1:-1:2,1).']; A_out_2 = circshift(outerIndices,mover,2) A_inner = [A(2,2:end-1), A(end-1, 2:end-1)]; ctr = 0; for ii = A(1, :) A_out(ii) = A_out_2(1,1:5); end A_out

I have now found all the numbers on the outer ring and the numbers in the inner ring. Can I use a loop to put these numbers in a place? or can I use the zeros function to make two arrays and add them together. I do not know where to go from here.

[Jan]

No, the outerIndices suggested by Matt J are indices, not the values as in your code. Stay at this code:

Values = A(outerIndices)
A(outerIndices) = ...

Now all you have to do is to insert the circshift 'ed Values instead of the "...". You do not need any loops.

[Gina Barlage]

When I did the above with the A(outerIndices) = circshift(outerindices,mover,2) I got this:

A =

    11     3     3     4    19
     6    16     4     9    20
     1    12    17     5    15
     2    17    18    18    10

[Walter Roberson]

Don't shift the indices, shift the content. See where I said "insert the circshift'ed Values"? Values, not indices

[Gina Barlage]

Ok I get it now thanks so much!

Answer 1

[Matt J]

As a hint, the following should give you the Linear Indices of the outer edges of the matrix in clockwise order,

   I=reshape(1:m*n,m,n);
   outerIndices=[I(1,:),I(2:end-1,end).',I(end,end:-1:1),I(end-1:-1:2,1).'];

[Gina Barlage]

Thanks so much! I understand how this works but how do I incorporate the outerindices and the inside of array A?

[Jan]

Values = A(outerIndices)
A(outerIndices) = ...