Display 3D graph for a function

Display a 3D graph for a function

x3 = 0;

nc=10;

y1 = 43.5943 - 12.5921*x1 + 4.08342*x2 + 3.6128*x3 + 14.4637* x1^2 + 9.3*x1*x2+ 4.1225*x1*x3 + 12.5333*x2^2 +3.2325* x2*x3+ 15.7648* x3^2;

[x1,x2] = meshgrid((1.68*(-1:1/nc:1)),(1.68*(-1:1/nc:1)));

mesh (x1,x2,y1)

But I got a figure which is not similar to the example.

How to display a function correctly?

Answer 1

[DGM]

You probably weren't intending to use matrix operations there.

x3 = 0; 
nc = 10;

[x1,x2] = meshgrid((1.68*(-1:1/nc:1)),(1.68*(-1:1/nc:1)));
% use .* and .^ for elementwise operations
y1 = 43.5943 - 12.5921*x1 + 4.08342*x2 + 3.6128*x3 ...
    + 14.4637*x1.^2 + 9.3*x1.*x2 + 4.1225*x1.*x3 ...
    + 12.5333*x2.^2 + 3.2325*x2.*x3 + 15.7648*x3.^2;
mesh (x1,x2,y1)

https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html