Color map plotting, Error using surf() Data dimensions must agree

I am trying to make a colour map plot using the following code:

    [x,z] = meshgrid(0:100:600,0:100:600);
    mm = size(z);
    for z2 = 1:3
        for x2 = 1:3
            E(z2,x2) = (x(x2))^2 + (z(z2))^2;
        end  
    end

    figure;
    surf(x,z,E,'EdgeColor','None');
    view(2);
    xlabel('x','fontsize',20);
    ylabel('z','fontsize',20);
    colormap jet

I used z2 and x2 in the for loop because I only want to use the first to third element in the meshgrid, which means, 0,100,200 for both x and z, but matlab returns me the error:

Error using surf (line 74) Data dimensions must agree.

Error in testgraph (line 10) surf(x,z,E,'EdgeColor','None');

But if I set z2 = 3:7 and x2 = 3:7, then it can produce a graph without an error, but I don't know why is this, and how can I achieve what I want to plot?

matlab error-handling colormap

Answer 1

[Walter Roberson]

x = 0:100:600;
z = 0:100:600;
x2 = 1:3;   %the indices of the subset you want to use
z2 = 1:3;   %the indices of the subset you want to use
x_chosen = x(x2);
z_chosen = z(z2);
[X, Z] = meshgrid( x_chosen, z_chosen );   %only create the meshgrid from the portion you need
E = X.^2 + Z.^2;
surf(X, Z, E)