def translate_coord(self, coord, log=_log):
"""Given a :class:`~data_model.DMCoordinate`, look up the corresponding
translated :class:`~data_model.DMCoordinate` in this convention.
"""
ax = coord.axis
if ax not in self.axes_lut:
raise KeyError(
f"Axis {ax} not defined in convention '{self.name}'.")
lut1 = self.axes_lut[ax] # abbreviate
if not hasattr(coord, 'standard_name'):
coords = tuple(lut1.values())
if len(coords) > 1:
raise ValueError(
(f"Coordinate dimension in convention '{self.name}' "
f"not uniquely determined by coordinate {coord.name}."))
new_coord = coords[0]
else:
if coord.standard_name not in lut1:
raise KeyError((
f"Coordinate {coord.name} with standard name "
f"'{coord.standard_name}' not defined in convention '{self.name}'."
))
new_coord = lut1[coord.standard_name]
if hasattr(coord, 'is_scalar') and coord.is_scalar:
new_coord = copy.deepcopy(new_coord)
new_coord.value = units.convert_scalar_coord(coord,
new_coord.units,
log=log)
else:
new_coord = dc.replace(coord,
**(util.filter_dataclass(new_coord, coord)))
return new_coord
def process(self, var, ds):
"""Determine if level extraction is needed, and return appropriate slice
of Dataset if it is.
"""
_atol = 1.0e-3 # absolute tolerance for floating-point equality
tv_name = var.name_in_model
our_z = var.get_scalar('Z')
if not our_z or not our_z.value:
_log.debug("Exit %s for %s: no level requested.",
self.__class__.__name__, var.full_name)
return ds
if 'Z' not in ds[tv_name].cf.dim_axes_set:
# maybe the ds we received has this level extracted already
ds_z = ds.cf.get_scalar('Z', tv_name)
if ds_z is None or isinstance(ds_z, xr_parser.PlaceholderScalarCoordinate):
_log.debug(("Exit %s for %s: %s %s Z level requested but value not "
"provided in scalar coordinate information; assuming correct."),
self.__class__.__name__, var.full_name, our_z.value, our_z.units)
return ds
else:
# value (on var.translation) has already been checked by
# xr_parser.DatasetParser
_log.debug(("Exit %s for %s: %s %s Z level requested and provided "
"by dataset."),
self.__class__.__name__, var.full_name, our_z.value, our_z.units)
return ds
# final case: Z coordinate present in data, so actually extract the level
ds_z = ds.cf.dim_axes(tv_name)['Z']
if ds_z is None:
raise TypeError("No Z axis in dataset for %s.", var.full_name)
try:
ds_z_value = units.convert_scalar_coord(our_z, ds_z.units)
ds = ds.sel(
{ds_z.name: ds_z_value},
method='nearest', # Allow for floating point roundoff in axis values
tolerance=_atol,
drop=False
)
_log.info("Extracted %s %s level from Z axis ('%s') of %s.",
ds_z_value, ds_z.units, ds_z.name, var.full_name)
# rename translated var to reflect renaming we're going to do
# recall POD variable name env vars are set on this attribute
var.translation.name = var.name
# rename dependent variable
return ds.rename({tv_name: var.name})
except KeyError:
# ds.sel failed; level wasn't present in coordinate axis
raise KeyError((f"Z axis '{ds_z.name}' of {var.full_name} didn't "
f"provide requested level ({our_z.value} {our_z.units}).\n"
f"(Axis values ({ds_z.units}): {ds_z.values})"))
except Exception as exc:
raise ValueError((f"Caught exception extracting {our_z.value} {our_z.units} "
f"level from '{ds_z.name}' coord of {var.full_name}.")) from exc