Unable to convert from Cartesian to cylindrical coords, 'mesh.CoordinateSystem.x' and 'mesh.CoordinateSystem.xR' return the same symbols (Cartesian) and underlying coordinates when evaluated.
import underworld3 as uw
mesh = uw.meshing.StructuredQuadBox(minCoords=(0,0), maxCoords=(1, 1), elementRes=(10,10) )
x, y = mesh.CoordinateSystem.x
r, th = mesh.CoordinateSystem.xR