Multiply nth elements of an array by an element of a different array?

I have the following code.

I would like it to work such that if the first element of Ox is greater than zero, which in this case it is, the 1st, 5th, 9th, 13th, 17th, 21st, 25th, etc up to the end of Array will be multiplied by the first element of Ox.

So the output would be:

AllOx1 = (0.5 1 1 1 0.5 1 1 1 0.5 1… etc)

Ox = [0.5 0 0 0];

Array = ones(1,256);
 
AllOx1 = [];

if Ox(1) > 0
    AllOx1 = (Array(1:4:end)*Ru(1), 1, []);
end

Any help would be much appreciated!

Thank you

[the cyclist]

I have a couple questions.

Your question does not mention the variable Ru, but your code uses it. Why?

What do you want AllOx1 to be if Ox is not greater than zero?

[Ashton Linney]

Ru is another variable I have in my code, but accidently included it here. Ru was meant to be Ox, which will have made a lot more sense for you, thank you for pointing that out to me :)

Answer 1

[dpb]

I'll presume the answer to Cyclist's 2nd Q? is to be unchanged...and the other is just using different variables for the posting...either way, the answer is essentially the one given removing some unnecessary fluff...but adding one critical piece:

A=ones(1,10);  Ox=[0.5 0 0];   % preliminaries...
% engine
B=A;                % must copy original else will be short unless mod(size(A),4)==0
if Ox(1)>0
  B(1:4:end)=B(1:4:end)*Ox(1);
end

>> B  % results...
B =
    0.5000    1.0000    1.0000    1.0000    0.5000    1.0000    1.0000    1.0000    0.5000    1.0000
>> 

[Ashton Linney]

That achieves exactly what I wanted it to. Thank you very much sir!

You were correct in your assumption :)

[dpb]

Occasionally the Crystal Ball Toolbox does come in handy... :)