code: def daily_temperature_range(tasmax, tasmin, freq='YS'):
      r
  
      dtr = tasmax - tasmin
      out = dtr.resample(time=freq).mean(dim='time', keep_attrs=True)
      out.attrs['units'] = tasmax.units
      return out
docs: r"""Mean of daily temperature range.
  
      The mean difference between the daily maximum temperature and the daily minimum temperature.
  
      Parameters
      ----------
      tasmax : xarray.DataArray
        Maximum daily temperature values [℃] or [K]
      tasmin : xarray.DataArray
        Minimum daily temperature values [℃] or [K]
      freq : str, optional
        Resampling frequency
  
      Returns
      -------
      xarray.DataArray
        The average variation in daily temperature range for the given time period.
  
      Notes
      -----
      Let :math:`TX_{ij}` and :math:`TN_{ij}` be the daily maximum and minimum temperature at day :math:`i`
      of period :math:`j`. Then the mean diurnal temperature range in period :math:`j` is:
  
      .. math::
  
          DTR_j = \frac{ \sum_{i=1}^I (TX_{ij} - TN_{ij}) }{I}