UnitsMapping#
- class astropy.modeling.mappings.UnitsMapping(mapping, input_units_equivalencies=None, input_units_allow_dimensionless=False, name=None, meta=None)[source]#
Bases:
Model
Mapper that operates on the units of the input, first converting to canonical units, then assigning new units without further conversion. Used by Model.coerce_units to support units on otherwise unitless models such as Polynomial1D.
- Parameters:
- mapping
tuple
A tuple of (input_unit, output_unit) pairs, one per input, matched to the inputs by position. The first element of the each pair is the unit that the model will accept (specify
dimensionless_unscaled
to accept dimensionless input). The second element is the unit that the model will return. Specifydimensionless_unscaled
to return dimensionless Quantity, andNone
to return raw values without Quantity.- input_units_equivalencies
dict
, optional Default equivalencies to apply to input values. If set, this should be a dictionary where each key is a string that corresponds to one of the model inputs.
- input_units_allow_dimensionless
dict
or bool, optional Allow dimensionless input. If this is True, input values to evaluate will gain the units specified in input_units. If this is a dictionary then it should map input name to a bool to allow dimensionless numbers for that input.
- name
str
, optional A human-friendly name associated with this model instance (particularly useful for identifying the individual components of a compound model).
- metadict-like, optional
Free-form metadata to associate with this model.
- mapping
Examples
Wrapping a unitless model to require and convert units:
>>> from astropy.modeling.models import Polynomial1D, UnitsMapping >>> from astropy import units as u >>> poly = Polynomial1D(1, c0=1, c1=2) >>> model = UnitsMapping(((u.m, None),)) | poly >>> model = model | UnitsMapping(((None, u.s),)) >>> model(u.Quantity(10, u.m)) <Quantity 21. s> >>> model(u.Quantity(1000, u.cm)) <Quantity 21. s> >>> model(u.Quantity(10, u.cm)) <Quantity 1.2 s>
Wrapping a unitless model but still permitting unitless input:
>>> from astropy.modeling.models import Polynomial1D, UnitsMapping >>> from astropy import units as u >>> poly = Polynomial1D(1, c0=1, c1=2) >>> model = UnitsMapping(((u.m, None),), input_units_allow_dimensionless=True) | poly >>> model = model | UnitsMapping(((None, u.s),)) >>> model(u.Quantity(10, u.m)) <Quantity 21. s> >>> model(10) <Quantity 21. s>
Attributes Summary
This property is used to indicate what units or sets of units the evaluate method expects, and returns a dictionary mapping inputs to units (or
None
if any units are accepted).The number of inputs.
The number of outputs.
Methods Summary
evaluate
(*args)Evaluate the model on some input variables.
Attributes Documentation
- input_units#
- inputs#
- mapping#
- n_inputs#
The number of inputs.
- n_outputs#
The number of outputs.
- outputs#
Methods Documentation