Affine symmetry groups represent translation. Isometries which leave the function unchanged are translations x + a with a such that f (x + a) = f (x) and reflections a − x with a such that f (a − x) = f (x). The reflections can be represented by the affine Coxeter group [∞], or Coxeter-Dynkin diagram representing two reflections, and the translational symmetry as [∞], or Coxeter-Dynkin diagram as the composite of two reflections.