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From: "Lorenzo Guerrasio" <lorenzo.guerrasio@email.it>
Newsgroups: comp.soft-sys.matlab
Subject: Re: Best fit ellipse given vertice and a few points
Date: Tue, 21 Oct 2008 13:29:02 +0000 (UTC)
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> Thanks for your reply John. To answer your questions, I want to fit the data with errors allowed for both x and y. The ellipse may be tilted if the data dictates it. The problem that I have is that Fitelllipse assumes (I think so anyway) that the data provided is spread around the ellipse to be approximated while what I have (5 points) belongs to only one of the quadrants. One additional point provided belongs to the vertex of the ellipse, adjacent to the 5 points provided. What I want is a best fit of an ellipse based on this data if it's possible.
> 
> Thanks for your time
> 
> Conrad


I'm not 100% sure,but I guess it would be licit, knowing that all the points belong only to one of the quadrant and knowing the vertex,to fit an ellipse with these points and the simmetrical rispect to the vertex. I think with this information you could fit the ellipse better. Use the information of the vertex to simplify the problem depends on which methods of fitting you are using.

REgards