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FIT_ELLIPSE [message #90730] Tue, 07 April 2015 12:18 Go to next message
samsammurphy is currently offline  samsammurphy
Messages: 2
Registered: March 2015
Junior Member
Hello,

The FIT_ELLIPSE program has been really useful for me!

I was wondering how to reference the technique used to calculate the major and minor axes?

The use of a 'mass distribution tensor' instead of the covariance of the data points seems novel to me (and computationally more efficient).

Many thanks,

Sam

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Re: FIT_ELLIPSE [message #90734 is a reply to message #90730] Tue, 07 April 2015 19:18 Go to previous messageGo to next message
David Fanning is currently offline  David Fanning
Messages: 11724
Registered: August 2001
Senior Member
samsammurphy@gmail.com writes:

> The FIT_ELLIPSE program has been really useful for me!
>
> I was wondering how to reference the technique used to calculate the major and minor axes?
>
> The use of a 'mass distribution tensor' instead of the covariance of the data points seems novel to me (and computationally more efficient).

Craig Markwardt did all the magic. I just carried his bags.

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")

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Re: FIT_ELLIPSE [message #90739 is a reply to message #90730] Wed, 08 April 2015 16:09 Go to previous message
Craig Markwardt is currently offline  Craig Markwardt
Messages: 1869
Registered: November 1996
Senior Member
On Tuesday, April 7, 2015 at 3:18:15 PM UTC-4, Sam Murphy wrote:
> Hello,
>
> The FIT_ELLIPSE program has been really useful for me!
>
> I was wondering how to reference the technique used to calculate the major and minor axes?
>
> The use of a 'mass distribution tensor' instead of the covariance of the data points seems novel to me (and computationally more efficient).


"Mass distribution tensor" is basically the same as the moments of the distribution, which is related to the covariance matrix. There's no magic here.

Craig

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