Question

I am trying to plot the following equation in MATLAB:

ratio = sqrt(1+1/(kr)^2)

With k and r on the x and y axes, and ratio on the z axis. I used meshgrid to create a matrix with values for x and y varying from 1 to 10:

[x,y] = meshgrid([1:1:10],[1:1:10]);

The problem now is to create values for z. I’ve tried to just type the whole equation in, but that gives this result:

>> Z = sqrt(1+1/(x .* y)^2)??? 
Error using ==> mldivide
Matrix dimensions must agree.

So what I did is go to through the whole process manually, which produces the right graph in the end:

z = z^2;
z = 1 ./ z;
z = 1 + z;
z = sqrt(z);
mesh(x,y,z)

Is there a more elegant way to do this? Or a way to type in the equation and let MATLAB handle the rest?

Answer 1

Try this:

 Z = sqrt(1+1./(x .* y).^2);
 surf(Z);

The problem that you had is related to using / instead of ./ and ^2 instead of .^2