Question

I’m working with a quadratic surface f(w0,w1) on MATLAB and I used meshgrid to create this. Here’s the code:

phi = 0.01;
M = 16;

[w0,w1] = meshgrid(-2:0.1:8 , -10:0.1:0);

f = (0.5+phi)*(w0.^2 + w1.^2) + w0.*w1*cos(2*pi/M) + 2*w1*sin(2*pi/M) + 2;

So I would like to know how can I obtain the value of the function f at the point (-1.9,-0.9), for example.

Thanks

Answer 1

You could either plug your values directly in the function f:

w0 = -1.9;
w1 = -0.9;
f = (0.5+phi)*(w0.^2 + w1.^2) + w0.*w1*cos(2*pi/M) + 2*w1*sin(2*pi/M) + 2;

or use indices on x and y:

x = -2:0.1:8;
y = -10:0.1:0;
[w0,w1] = meshgrid(x, y);
f = (0.5+phi)*(w0.^2 + w1.^2) + w0.*w1*cos(2*pi/M) + 2*w1*sin(2*pi/M) + 2;
f(find(y==-0.9), find(x==-1.9));

Both methods will return:

ans =
5.1452