How do I vectorise a for loop that reorders 4 bytes of an array with each iteration

A = uint8(Data); %Assume the data comes in multiples of 4 bytes

B = [];

for byteNo = 1 :4: length(A)-3 % changed 4  to 3 to fix the typo that was flagged by Walter Roberson

   B = cat(2,B,[A(byteNo+2),A(byteNo+3),A(byteNo),A(byteNo+1)]);

end

[Walter Roberson]

I suspect the termination should be length(A)-3 rather than -4 . Consider that if A was length 8, then there would be room for two swaps of length 4, but your upper bound would be byteNo = 4 which is before the second lower byteNo needed for the swap, which has to start at byteNo = 5.

Answer 1

[Walter Roberson]

If the vector is not a multiple of length 4, discard mod(length,4) values from the end of it. Take the resulting vector and reshape() it into 4 rows. Reorder the rows. Reshape the result into a vector.

[Scorp]

Thank you for your help. That works really well.