Creation of matrix from loop

The following is a code for creation of matrix using for loop

 for r = 1:256;
 for c=1:256;
    m(r,c) = (r+c)^2;
 end;
end;
disp(m)

In m(r,c) = (r+c)^2; Suppose, if there are two or more equations like (r+c)^2 and (2r-c)^2 and (r+3c) ,I want to get m(r1,c1)=(r+c)^2 and m(r2,c2)=(2r-c)^2 and m(r3,c2)=(r+3c) and again m(r4,c4)=(r+c)^2 and m(r5,c5)=(2r-c)^2 and ...... etc upto m(r256,c256).

Answer 1

[Star Strider]

I am not certain what you want to do, and you do not say what ‘(r2,c2)’ and the rest are, or what you want to do with them.

You can eliminate the loop with meshgrid:

r = 1:256;
c = 1:256;
[R,C] = meshgrid(r,c);
m = (R + C).^2;

figure(1)
meshc(R, C, m)
grid on
xlabel('\bf\itr')
ylabel('\bf\itc')
zlabel('\bf\itm')

[Renjith V Ravi]

How to merge this r and c to form a matrix of size 256x256

[Star Strider]

Your ‘m’ matrix already is (256x256).

Check:

m_size = size(m)

m_size =
   256   256

[Renjith V Ravi]

Yes, But m = (R+C).^2 . I just want to merge r and c to form a matrix of size 256x256

[Star Strider]

My code does exactly that, without the loop.

Run my code and compare the figure it produces (in figure(1)) with the figure your code produces (in figure(2)):

for r = 1:256;
    for c=1:256;
        m(r,c) = (r+c)^2;
    end;
end;

figure(2)
meshc(m)
grid on

The result is the same, the only difference being that my code is more efficient and easier to work with.