code: def to_pfull_from_phalf(arr, pfull_coord):
      
      phalf_top = arr.isel(**{internal_names.PHALF_STR: slice(1, None)})
      phalf_top = replace_coord(phalf_top, internal_names.PHALF_STR,
                                internal_names.PFULL_STR, pfull_coord)
  
      phalf_bot = arr.isel(**{internal_names.PHALF_STR: slice(None, -1)})
      phalf_bot = replace_coord(phalf_bot, internal_names.PHALF_STR,
                                internal_names.PFULL_STR, pfull_coord)
      return 0.5*(phalf_bot + phalf_top)
docs: Compute data at full pressure levels from values at half levels.