在MATLAB中绘制多变量函数图

Question

I have never used MATLAB before, so I am very lost. For my calculus class, we were tasked with finding a certain function and then using MATLAB to graph it. Finding the function was no problem. However, trying to graph it has me pulling my hair out. The function is z(x,y)= xy(x+y)(2x+y)(3x+y)(x-2y)(x-3y)(x-4y). Any help or advice is GREATLY appreciated.

Answer 1

You can define a anonymous function handle.

% define function
% .* denotes element wise multiplication
f = @(x,y) x.*y.*(x+y).*(2*x+y).*(3*x+y).*(x-2*y).*(x-3*y).*(x-4*y);

% define range and resolution for x and y
x = -20:0.5:20;
y = -20:0.5:20;

% create meshgrid for 3d plotting
[X, Y] = meshgrid(x,y);

% calculate z values (for meshgrid)
z = f(X, Y);

% plot the function
figure()
surf(x,y,z)

To explain further, since you want to calculate the z value for x and y pairs, you should use a element wise multiplication .* .

Then you have to create a meshgrid for the x and y values, to have all the possible x and y pairs in the two new matrices X and Y . Providing these to your function will calculate the corresponding z value for all these pairs. You can use these for plotting, eg surf.