code: def residuals(self):
          
          _ = self.rotated()
          _[:,-1] = 0
          _ = N.dot(_,self.axes)
          return self.arr - _
docs: Returns residuals of fit against all
          three data axes (singular values 1, 2,
          and 3). This takes the form of data along
          singular axis 3 (axes 1 and 2 define the plane)