Plot z = x^2 + y^2 over the interval -4 <= x <= +4, -4 <= y <= +4.

I'm not sure how to plot above equation. Can anyone help me?

Answer 1

[KSSV]

N = 100 ;
x = linspace(-4,4,N) ;
y = linspace(-4,4,N) ;

[X,Y] = meshgrid(x,y) ;
Z = X.^2+Y.^2 ;

surf(X,Y,Z)

[Dane Kim]

Hi, you had N = 100;. What does the "N" do? sorry I'm new to matlab.

[KSSV]

You can very it to have those many points along axes.

[Dane Kim]

oh okay, so it is arbitrary. I can have 100 - 10000 or more.

[Image Analyst]

Correct, but don't do more than you can see any difference for. Yours is such a smooth function it doesn't make sense to do many more points. If you do, the edge lines will ruin the colors.

You can turn off the black edge lines like this:

surf(X,Y,Z, 'EdgeColor', 'none')

Answer 2

[Stephan]

Hi,

use:

syms x y
f(x,y) = x^2 + y^2;
fsurf(f, [-4 4 -4 4])

Note that this will work if you have access to th Symbolic Math Toolbox. If you dont have it, the answer from KSSV will always work.

Best regards

Stephan