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Topic: Ellipe drawing
Replies: 2   Last Post: Jun 21, 2013 6:06 PM

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Derek Goring

Posts: 3,894
Registered: 12/7/04
Re: Ellipe drawing
Posted: Jun 21, 2013 5:35 PM
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On Friday, June 21, 2013 10:16:09 PM UTC+12, aalcaineo wrote:
> Hello all
>
>
>
> I'm trying to draw an ellipse in the same fashion I did it for a circle, I let you an example
>
>
>
> [X,Y] = meshgrid(0:1/SpatSamp:Xmax,0:1/SpatSamp:Ymax);
>
> Act = sqrt((X-Loc(1)).^2+(Y-Loc(2)).^2);
>
>
>
> where SpatSamp is the spatial sampling, Xmax and Ymax are the limits y Loc is a vector with the X,Y coordinates of the center.
>
>
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> the objective is to plot it using "contour"
>
>
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> Any ideas? thank you in advance for your help!


That's a weird way of plotting an ellipse.

Here's an alternative for an ellipse with major axis qmax and minor axis qmin, centre at x0,y0, and orientated theta deg from N.
function [x,y]=ellipse(qmax,qmin,theta,x0,y0,n)
%
% Set up parameters
%
theta=theta*pi/180; % Orientation from N
wt=0:n; % n is no of points 180 is good
dwt=2*pi/n;
wt=wt'*dwt;
sth=sin(theta);
cth=cos(theta);
%
% Calculate ellipse with zero orientation
%
x1=qmax*cos(wt);
y1=qmin*sin(wt);
%
% Orientate theta deg from north
%
x=x1*sth-y1*cth+x0;
y=x1*cth+y1*sth+y0;

plot(x,y)



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