code: def _evaluate(self,x,y):
          '''
          Returns the level of the interpolated function at each value in x,y.
          Only called internally by HARKinterpolator2D.__call__ (etc).
          '''
          x_pos, y_pos = self.findSector(x,y)
          alpha, beta = self.findCoords(x,y,x_pos,y_pos)
  
          # Calculate the function at each point using bilinear interpolation
          f = (
               (1-alpha)*(1-beta)*self.f_values[x_pos,y_pos]
            +  (1-alpha)*beta*self.f_values[x_pos,y_pos+1]
            +  alpha*(1-beta)*self.f_values[x_pos+1,y_pos]
            +  alpha*beta*self.f_values[x_pos+1,y_pos+1])
          return f _evaluate(self,x,y):
          '''
          Returns the level of the interpolated function at each value in x,y.
          Only called internally by HARKinterpolator2D.__call__ (etc).
          '''
          x_pos, y_pos = self.findSector(x,y)
          alpha, beta = self.findCoords(x,y,x_pos,y_pos)
  
          # Calculate the function at each point using bilinear interpolation
          f = (
               (1-alpha)*(1-beta)*self.f_values[x_pos,y_pos]
            +  (1-alpha)*beta*self.f_values[x_pos,y_pos+1]
            +  alpha*(1-beta)*self.f_values[x_pos+1,y_pos]
            +  alpha*beta*self.f_values[x_pos+1,y_pos+1])
          return f
docs: Returns the level of the interpolated function at each value in x,y.
          Only called internally by HARKinterpolator2D.__call__ (etc).