docs: def plot(self, ifig=1, data_label='data', fit_label='fit',
               data_shape='o', fit_shape='-'):
          '''
          plot the data and the fitted function.
  
          Parameters
          ----------
          ifig : integer
              Figure window number.  The default is 1.
          data_label : string
              Legend for data.  The default is 'data'.
          fit_label : string
              Legend for fit.  If fit_lable is 'fit', then substitute fit
              function type self.func_name.  The default is 'fit'.
          data_shape : character
              Shape for data.  The default is 'o'.
          fit_shape : character
              Shape for fit.  The default is '-'.
  
          '''
  
          if len(self.coef) is not len(self.fcoef):
              print("Warning: the fitted coefficient list is not same")
              print("         length as guessed list - still I will try ...")
  
          pl.figure(ifig)
          pl.plot(self.x,self.y,data_shape,label=data_label)
          if fit_label is 'fit':
              fit_label=self.__name__
          pl.plot(self.x,self.func(self.fcoef,self.x),fit_shape,label=fit_label)
          pl.legend()