RF: Rectify to non-negative only optionally.
RF: Rectify to non-negative only optionally.

matthieudumont/dipy,matthieudumont/dipy,FrancoisRheaultUS/dipy,FrancoisRheaultUS/dipy,JohnGriffiths/dipy,JohnGriffiths/dipy,villalonreina/dipy,nilgoyyou/dipy,StongeEtienne/dipy,StongeEtienne/dipy,nilgoyyou/dipy,villalonreina/dipy