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Re: fitting contours with ellipse [message #69343 is a reply to message #69341]

Tue, 05 January 2010 03:22

fburton
Messages: 19
Registered: June 2003

Junior Member

In article <2219a304-4c24-4d4d-ab33-4e8c2dce92de@m25g2000yqc.googlegroups.com>,
collinritzinger <b0burk02@gmail.com> wrote:
> I have several contour maps and I'd like to have a more quantitative
> way of describing how 'peaked' or 'boxy/circular' they are. I was
> thinking of doing this by fitting an ellipse to the contours and
> examining best fit parameters. People have done this for blobs before
> (see http://www.dfanning.com/ip_tips/fit_ellipse.html) but I'm not so
> sure how to go about it for contours. Do you all have any ideas?
> Thanks!

One requirement for a 'good fit' in this case is to have as
much of the ellipse represented by data points as possible
(i.e. no big gaps). The set of coordinates returned by CONTOUR
using the PATH_INFO keyword should be well-spaced at least;
whether there are enough coordinates will depend on the size
of the contour path in relation to the grid spacing. I would
simply feed the coordinates to the ellipse-fitting routine
and see if it produces sensible results for your data.

Francis

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[Message index]

		Re: fitting contours with ellipse By: fburton on Tue, 05 January 2010 07:55
		Re: fitting contours with ellipse By: David Fanning on Tue, 05 January 2010 05:02
		Re: fitting contours with ellipse By: fburton on Tue, 05 January 2010 03:22
		Re: fitting contours with ellipse By: natha on Fri, 08 January 2010 10:24

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