How to delete multiple elements of an array using for loop?

I have an array x which is equal to [1:40000]. In every 1000 elements I am trying to delete the first 500 elements I cannot figure this out for the life of me, I think it should look something like x(for loop)=[] I would greatly appreciate help from anyone!

Answer 1

[Akira Agata]

You don't need to use for-loop. Please try the following:

idx = mod(x-1,1000) < 500;
x(idx)=[];

[Jose Camorlinga Medina]

 I appreciate the help.