Re: A question on algebraic circle fitting



Thomas Mautsch wrote:

Given a finite number of points in the plane, (x1,y1), (x2,y2), ..., (xn,yn), the "algebraic way" to fit a circle to these points is to minimize the sum

sum( (xi^2 + yi^2 + 2 D xi + 2 E yi + F)^2 , i = 1..n )

over the variables D,E,F.

Is it correct that the resulting minimizers will satisfy the condition

D^2 + E^2 >= F ?

Under what conditions will minimizers D,E,F exist? - A necessary condition is that not all points (xi,yi) lie on a common line in case n >= 3. Is this condition also sufficient, or what other conditions are there?

http://huizen.dto.tudelft.nl/deBruijn/programs/delphi.htm#BFC

Read the paragraph "Method by RI" (: Robert Israel). Yes, it is correct
that the resulting minimizers will satisfy the condition D^2 + E^2 >= F
as far as I can see.

Han de Bruijn

.



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