Re: A question on algebraic circle fitting



In article <1161652895.263299.29890@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
anon5874@xxxxxxxxx wrote:

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?

Wouldn't 3 points specify the circle uniquely?

Not if they are colinear.
.



Relevant Pages

  • Re: circle fit to array with error term
    ... I need to fit the largest possible radius circle to the ... First sum the pixel values of each image to get a total intensity ... I also tried closed spline fit, but had some trouble with consistency ...
    (comp.soft-sys.matlab)
  • Re: A question on algebraic circle fitting
    ... the "algebraic way" to fit a circle to these points is to minimize the sum ... Under what conditions will minimizers D,E,F exist? ...
    (sci.math)
  • Re: A question on algebraic circle fitting
    ... the "algebraic way" to fit a circle to these points ... is to minimize the sum ... Under what conditions will minimizers D,E,F exist? ...
    (sci.math)
  • Re: A question on algebraic circle fitting
    ... the "algebraic way" to fit a circle to these points ... is to minimize the sum ... Under what conditions will minimizers D,E,F exist? ... Wouldn't 3 points specify the circle uniquely? ...
    (sci.math)
  • Re: A question on algebraic circle fitting
    ... the "algebraic way" to fit a circle to these points ... is to minimize the sum ... Under what conditions will minimizers D,E,F exist? ...
    (sci.math)

Loading