Question: How to fit a circle to a set of points?

Hello everyone!

I have a question that I can't seem to find a straight answer to. I need to fit a circle to a collection of points that a circular in nature. I was trying to use the following elliptical least squares fit, but I can't determine what I should be minimizing.

Here's the page:

http://www.maplesoft.com/applications/view.aspx?SID=1395&view=html

 

For an ellipse, I used the general conic:

F:=a*x^2+b*x*y+c*y^2+d*x+e*y+f

I minimize using:

V:=Minimize(E,{4*a*c-b^2=1});

 

What would I use for a circle? Or is there a better way for a circle?

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