fixed deprecated affine_hull; improved doc

Author: Jonathan Kliem

src/sage/geometry/polyhedron/base.py

@@ -2755,6 +2755,9 @@ def centroid(self, engine='auto', **kwds):
         The mass is taken with respect to the induced Lebesgue measure,
         see :meth:`volume`.
 
+        If the polyhedron is not compact, a ``NotImplementedError`` is
+        raised.
+
         INPUT:
 
         - ``engine`` -- either 'auto' (default), 'internal',
@@ -2768,9 +2771,6 @@ def centroid(self, engine='auto', **kwds):
 
         OUTPUT: The centroid as vector.
 
-        If the polyhedron is not compact, a ``NotImplementedError`` is
-        raised.
-
         ALGORITHM:
 
         We triangulate the polytope and find the barycenter of the simplices.
@@ -2823,7 +2823,7 @@ def centroid(self, engine='auto', **kwds):
             pc = triangulation.point_configuration()
         else:
             from sage.geometry.triangulation.point_configuration import PointConfiguration
-            A,b = self.affine_hull(as_affine_map=True, orthogonal=True, orthonormal=True, extend=True)
+            A,b = self.affine_hull_projection(as_affine_map=True, orthogonal=True, orthonormal=True, extend=True)
             pc = PointConfiguration((A(v.vector()) for v in self.Vrep_generator()))
 
         barycenters = [sum(self.Vrepresentation(i).vector() for i in simplex)/(self.dim() + 1) for simplex in triangulation]