🚀 go-pugleaf

You can't specify y in terms of x, because a circle is not a function
(one x can map to 2 different values of y).  Instead, use a "fake" dependent
variable with the value zero, and on the right hand side, write the function
to be minimized (when squared).  This approach will work for any nonlinear
least squares package.  In your case, let's say the circle's origin is
(A,B) with radius R.  Dependent variable:  ZERO=0;
Function for PROC NLIN:  ZERO = R - SQRT((X-A)**2 + (Y-B)**2)

Clint Cummins