Plotting an Ellipse

I'm trying to draw a 2D ellipse. I know that I can use the rectangle function and set the curvature equal to 1, but I came across this page http://www.mathworks.com/help/toolbox/mupad/plot/PRIMITIV_Ellipse2d.html, and I was wondering how I would implement it. It looks like it could be very useful, but whenever I try it says it cannot recognize the char inputs.

[Walter Roberson]

Could you show us a sample of how you are invoking that routine?

Answer 1

[David Legland]

Hi,

Maybe the best way to draw an ellipse is to use its parametric form:

% compute points corresponding to axis-oriented ellipse
t = linspace(0, 2*pi, 200);
xt = r1 * cos(t) + xc;
yt = r2 * sin(t) + yc;
% aply rotation by angle theta
cot = cos(theta); sit = sin(theta);
x = xt * cot - yt * sit;
y = xt * sit - yt * cot;
% draw the curbe
plot(x, y, '-');

This can be easily converted to a single function.

[Nshine]

Minor typo in the rotation:

replace

y = xt * sit - yt * cot;

with

y = xt * sit + yt * cot;