How to plot an elliptical surface in Matlab?

Hello there,

Is there a way to plot an elliptical surface (elliptical plate) in Matlab? I've tried the code below (among other codes), but instead of an ellipse, I get a squared shape (I think it is because of meshgrid).

a= 8; b = 6; x=linspace(-a,a,60); y = b*sqrt(1-(x./a).^2);

x = [x; x(length(x):-1:1)]; y = [-y, y];

[x,y]=meshgrid(x,y);

%y = b*sqrt(1-(x./a).^2);

z = ones(size(x));

surface(x,y,z)

Thank you,

Answer 1

[Joseph Cheng]

depending on what you want to do with it matlab has the function

[x, y, z] = ellipsoid(0,0,0,8,6,3.25,30);

you'll only need half of the generated ellipsoid and you can flatten z to be 1.

Answer 2

[Andrew Newell]

You have defined the perimeter of an ellipse, and meshgrid just turns it into a square grid. The command patch allows you to plot your ellipse and fill it with your color of choice.

a= 8; b = 6; x=linspace(-a,a,60); y = b*sqrt(1-(x./a).^2);
x = [x fliplr(x)]; y = [-y y]; z = ones(size(x));
patch(x,y,z,'g')
axis equal

The command axis equal ensures that the ellipse has its true shape and is not distorted by the scale.

Here is another example where z varies and the view is specified:

a= 8; b = 6; x=linspace(-a,a,60); y = b*sqrt(1-(x./a).^2);
x = [x fliplr(x)]; y = [-y y]; z = sin(x);
patch(x,y,z,'g')
axis equal
view(18,22)

Answer 3

[fernanr5]

Thank you for your response. The problem is that z is actually a function of x and/or y. So say z=sin(x). In the code I set z = 1 just as an example, but I really want it to vary with x and y.

Appreciate your help.

Answer 4

[fernanr5]

Thanks for your response. However, I am looking for a 3D plot (surface plot).

Thank you,

[Andrew Newell]

It is 3D. You can rotate the axes using the rotate tool in the plot window or using view.

Please note that it is less confusing to use "Comment on this Answer" to respond to a particular answer.