🚀 go-pugleaf

Concerning fitting a circle to data points, recently 
	ritley@uimrl7.mrl.uiuc.edu 
posted a message with the program FELLIPSE that fits an ellipse.
Instead of posting again the program FCIRCLE let me just mention that 
a small modification to FELLIPSE fits circles by minimizing 
        sum( (X_i^2+Y_i^2 + d X_i + e Y_i + f)^2 )
The result is invariant by translation & rotation of the data points.

The following construction of the data matrix in FELLIPSE
> C     Building the matrices A and B 
> C
>       DO 10 I = 1, N
>         A(I,1) = X(I)**2-Y(I)**2
>         A(I,2) = X(I)*Y(I)
>         A(I,3) = X(I)
>         A(I,4) = Y(I)
>         A(I,5) = 1. 
>    10   B(I) = -(X(I)**2+Y(I)**2)
> C

should be replaced by 

> C     Building the matrices A and B 
> C
>       DO 10 I = 1, N
>         A(I,1) = X(I)
>         A(I,2) = Y(I)
>         A(I,3) = 1. 
>    10   B(I) = -(X(I)**2+Y(I)**2)

and B(1), B(2), and B(3) are d, e, and f after the call to HFTI.

I can email FCIRCLE if this is not clear enough. 

	Daniel Pfenniger