Question

X=(-5:.5:5)
Z=(-3:.5:3)
[x z]=meshgrid(X,Z)

The cutoff function that must delete the wanted elements is a circle with radius 1
(x-1)^2+(z-1)^2<=1
How can we manage a loop to put those elements 0 in the output data?

Answer 1

I think what you are looking for is this:

for i=1:size(x,1)
   for j=1:size(x,2)
      if ((x(i,j)-1)^2+(z(i,j)-1)^2<=1)
          x(i,j) = 0;
          y(i,j) = 0;
      end
   end
end

I hope this code is easy enough for you to understand what it does – if not you should take a programming class somewhere or sit down with a book.

Now, if the above answer is what you were looking for, take my word for it that gnovice’s answer (a mix of edit 2 and edit 3 actually) showed the way how to do this much smarter in MATLAB:

radius = 1;
index = (x-1).^2 + (z-1).^2 <= radius^2;  %# Logical index of elements inside the circle
x(index) = 0;  %# Set the x values inside the circle to 0
z(index) = 0;  %# Set the z values inside the circle to 0

Hope this helps – otherwise I’m giving up ;-).