Merge pull request #851 from compas-dev/bestfit_circle_redux

Avoid stable points

Author: beverlylytle

CHANGELOG.md

@@ -21,9 +21,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * Allow str or int as joint type in `compas.robots.Joint` constructor.
 * `compas_ghpython.artists.FrameArtist.draw` now draws a Rhino Plane.
+* Fixed bugs in `compas.geometry.bestfit_circle_numpy`.
 * Changed directory where ghuser components are installed.
 * Added ghuser components directory to those removed by the `clean` task.
-* Fixed bug in `compas.geometry.bestfit_circle_numpy`.
 
 ### Removed
 

src/compas/geometry/bestfit/bestfit_numpy.py

@@ -4,7 +4,6 @@
 
 from numpy import asarray
 from numpy import sqrt
-from numpy import mean
 from numpy import zeros
 from numpy.linalg import lstsq
 from scipy.optimize import leastsq
@@ -122,8 +121,10 @@ def f(c):
         Ri = dist(*c)
         return Ri - Ri.mean()
 
-    xm = mean(x)
-    ym = mean(y)
+    # The mean of x and y are very nearly 0 (1.0e-15), which reveals a numerical
+    # instability of the problem.  So, we choose our initial guess
+    # to be an epsilon bigger than that.
+    xm = ym = 0.00001
     c0 = xm, ym
     c, error = leastsq(f, c0)