Can I use the fit() function to fit an ellipse on x,y data (covers only a part of the ellipse, not equally distributed around it) ? Could you please tell me how to do this? Thank you!

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Istvan 2017-7-19

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https://ww2.mathworks.cn/matlabcentral/answers/349389-can-i-use-the-fit-function-to-fit-an-ellipse-on-x-y-data-covers-only-a-part-of-the-ellipse-not-e

评论： Istvan 2017-7-19

Can I use the fit() function to fit an ellipse on x,y data (covers only a part of the ellipse, not equally distributed around it) ? Could you please tell me how to do this?

I cannot enter the equation to fit() because the equation of an ellipse ( (x-x0)^2/(a^2) + (y-y0)^2/(b^2) = 1 ) cannot be brought to a y = f(x) form...

If I cannot do it by fit(), is there ant other simple way?

I need: the center (x0,y0), the equation and the peak value (highest y).

Thank you!

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Istvan 2017-7-19

fit_ellipse() ( https://uk.mathworks.com/matlabcentral/fileexchange/3215-fit-ellipse ) fails, saying: Warning: Matrix is singular, close to singular or badly scaled. Results may be inaccurate. RCOND = NaN. > In fit_ellipse (line 155) stopped because of a warning regarding matrix inversion

... and

EllipseDirectFit ( http://uk.mathworks.com/matlabcentral/fileexchange/22684-ellipse-fit--direct-method- ) will not work, as this solution expects to have data all around the ellipse. I only have data on about 30% of it.

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