xarray.Dataset.pint.quantify

Dataset.pint.quantify(units=<object object>, unit_registry=None, **unit_kwargs)

Attach units to the variables of the Dataset.

Units can be specified as a pint.Unit or as a string, which will be parsed by the given unit registry. If no units are specified then the units will be parsed from the "units" entry of the Dataset variable’s .attrs. Will raise a ValueError if any of the variables already contain a unit-aware array with a different unit.

Note

Be aware that unless you’re using dask this will load the data into memory. To avoid that, consider converting to dask first (e.g. using chunk).

Warning

As units in dimension coordinates are not supported until xarray changes the way it implements indexes, these units will be set as attributes.

Parameters

  • units (mapping of hashable to unit-like, optional) – Physical units to use for particular DataArrays in this Dataset. It should map variable names to units (unit names or pint.Unit objects). If not provided, quantify will try to read them from Dataset[var].attrs['units'] using pint’s parser. The "units" attribute will be removed from all variables except from dimension coordinates.

  • unit_registry (pint.UnitRegistry, optional) – Unit registry to be used for the units attached to each DataArray in this Dataset. If not given then a default registry will be created.

  • **unit_kwargs – Keyword argument form of units.

Returns

quantified – Dataset whose variables will now contain Quantity arrays with units.

Return type

Dataset

Notes

"none" and None can be used to mark variables that should not be quantified.

Examples

>>> ds = xr.Dataset(
...     {"a": ("x", [0, 3, 2], {"units": "m"}), "b": ("x", [5, -2, 1])},
...     coords={"x": [0, 1, 2], "u": ("x", [-1, 0, 1], {"units": "s"})},
... )

>>> ds.pint.quantify()
<xarray.Dataset>
Dimensions:  (x: 3)
Coordinates:
  * x        (x) int64 0 1 2
    u        (x) int64 [s] -1 0 1
Data variables:
    a        (x) int64 [m] 0 3 2
    b        (x) int64 5 -2 1
>>> ds.pint.quantify({"b": "dm"})
<xarray.Dataset>
Dimensions:  (x: 3)
Coordinates:
  * x        (x) int64 0 1 2
    u        (x) int64 [s] -1 0 1
Data variables:
    a        (x) int64 [m] 0 3 2
    b        (x) int64 [dm] 5 -2 1

Don’t quantify specific variables:

>>> ds.pint.quantify({"a": None})
<xarray.Dataset>
Dimensions:  (x: 3)
Coordinates:
  * x        (x) int64 0 1 2
    u        (x) int64 [s] -1 0 1
Data variables:
    a        (x) int64 0 3 2
    b        (x) int64 5 -2 1

Quantify with the same unit:

>>> q = ds.pint.quantify()
>>> q
<xarray.Dataset>
Dimensions:  (x: 3)
Coordinates:
  * x        (x) int64 0 1 2
    u        (x) int64 [s] -1 0 1
Data variables:
    a        (x) int64 [m] 0 3 2
    b        (x) int64 5 -2 1
>>> q.pint.quantify({"a": "m"})
<xarray.Dataset>
Dimensions:  (x: 3)
Coordinates:
  * x        (x) int64 0 1 2
    u        (x) int64 [s] -1 0 1
Data variables:
    a        (x) int64 [m] 0 3 2
    b        (x) int64 5 -2 1