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Wed, 01 Jun 2011 01:37:02 +0000
Ellipse plot
http://www.mathworks.com/matlabcentral/newsreader/view_thread/308573#838789
Isadora
Hi so I was wondering how you would go about plotting an ellipse on matlab, but I want it to have nodes at set intervals around the ellipse that I would be able to control.<br>
What I have right now is a bunch of nodes that I have connected by straight lines imitating an ellipse, but I would like to have smooth lines and evenly spaced nodes. How would I be able to do that?<br>
Thanks

Wed, 01 Jun 2011 02:06:44 +0000
Re: Ellipse plot
http://www.mathworks.com/matlabcentral/newsreader/view_thread/308573#838793
TideMan
On Jun 1, 1:37 pm, "Isadora " <ical1...@gmail.com> wrote:<br>
> Hi so I was wondering how you would go about plotting an ellipse on matlab, but I want it to have nodes at set intervals around the ellipse that I would be able to control.<br>
> What I have right now is a bunch of nodes that I have connected by straight lines imitating an ellipse, but I would like to have smooth lines and evenly spaced nodes. How would I be able to do that?<br>
> Thanks<br>
<br>
Show us what you've got now, then.<br>
If you've done it correctly, you should simply be able to increase the<br>
number of angular increments around the 360 deg. to get a smoother<br>
curve.

Wed, 01 Jun 2011 02:25:14 +0000
Re: Ellipse plot
http://www.mathworks.com/matlabcentral/newsreader/view_thread/308573#838795
Roger Stafford
"Isa" wrote in message <is453u$sno$1@newscl01ah.mathworks.com>...<br>
> Hi so I was wondering how you would go about plotting an ellipse on matlab, but I want it to have nodes at set intervals around the ellipse that I would be able to control.<br>
> What I have right now is a bunch of nodes that I have connected by straight lines imitating an ellipse, but I would like to have smooth lines and evenly spaced nodes. How would I be able to do that?<br>
> Thanks<br>
        <br>
It is easy make a plot of an ellipse. Surprisingly it is not so easy to place precisely evenlyspaced points around its circumference. This problem is I believe the source of the name "elliptic integrals". The total arclength requires the solution of an elliptic integral of the second kind, complete. The arclength to arbitrary points on it requires an elliptic integral of the second kind, incomplete.<br>
<br>
You can read about it at the Wikipedia site:<br>
<br>
<a href="http://en.wikipedia.org/wiki/Elliptic_integral">http://en.wikipedia.org/wiki/Elliptic_integral</a><br>
<br>
Matlab's Symbolic Toolbox contains a MuPAD function called 'EllipticE' that can solve such problems. Read about it at:<br>
<br>
<a href="http://www.mathworks.com/help/toolbox/symbolic/mfunlist.html">http://www.mathworks.com/help/toolbox/symbolic/mfunlist.html</a><br>
<br>
Roger Stafford

Wed, 01 Jun 2011 02:33:39 +0000
Re: Ellipse plot
http://www.mathworks.com/matlabcentral/newsreader/view_thread/308573#838798
ImageAnalyst
Isadora:<br>
You might try John D'Errico's interparc:<br>
<br>
<a href="http://www.mathworks.com/matlabcentral/fileexchange/27096interparc">http://www.mathworks.com/matlabcentral/fileexchange/27096interparc</a><br>
<br>
Description<br>
<br>
I've occasionally gotten requests for the ability to interpolate a 2d<br>
curve (or a general space curve) as a function of arc length,<br>
returning points that are now equally spaced in arc length, where<br>
originally the points had an arbitrary spacing.<br>
<br>
This is a simple thing to do if you are willing to use a piecewise<br>
linear interpolant. More difficult is when the curve is a parametric<br>
spline or pchip model. The interparc.m function uses an ode solver to<br>
integrate the distance along the curve itself, then uses that ode<br>
solver to do the interpolation.<br>
<br>
For example, generate a set of unequally spaced points around the<br>
perimeter of a unit circle.<br>
<br>
<br>
etc. . . . . . .