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FEAT: with_spectral_axis_and_flux_units #1184

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Oct 14, 2024
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FEAT: with_spectral_axis_and_flux_units #1184

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3 changes: 3 additions & 0 deletions CHANGES.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,9 @@
New Features
^^^^^^^^^^^^

- New ``Spectrum1D.with_spectral_axis_and_flux_units`` method to convert both
spectral axis and flux units at the same time. [#1184]

Bug Fixes
^^^^^^^^^

Expand Down
71 changes: 45 additions & 26 deletions specutils/spectra/spectrum_mixin.py
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Expand Up @@ -86,6 +86,26 @@ def new_flux_unit(self, unit, equivalencies=None, suppress_conversion=False):
return self.with_flux_unit(unit, equivalencies=equivalencies,
suppress_conversion=suppress_conversion)

def _convert_flux(self, unit, equivalencies=None, suppress_conversion=False):
"""This is always done in-place.
Also see :meth:`with_flux_unit`."""

if not suppress_conversion:
if equivalencies is None:
equivalencies = eq.spectral_density(self.spectral_axis)

new_data = self.flux.to(unit, equivalencies=equivalencies)

self._data = new_data.value
self._unit = new_data.unit
else:
self._unit = u.Unit(unit)

if self.uncertainty is not None:
self.uncertainty = StdDevUncertainty(
self.uncertainty.represent_as(StdDevUncertainty).quantity.to(
unit, equivalencies=equivalencies))

def with_flux_unit(self, unit, equivalencies=None, suppress_conversion=False):
"""Returns a new spectrum with a different flux unit.
If uncertainty is defined, it will be converted to
Expand All @@ -107,30 +127,14 @@ def with_flux_unit(self, unit, equivalencies=None, suppress_conversion=False):

Returns
-------
`~specutils.Spectrum1D`
new_spec : `~specutils.Spectrum1D`
A new spectrum with the converted flux array
(and uncertainty, if applicable).

"""
new_spec = deepcopy(self)

if not suppress_conversion:
if equivalencies is None:
equivalencies = eq.spectral_density(self.spectral_axis)

new_data = self.flux.to(
unit, equivalencies=equivalencies)

new_spec._data = new_data.value
new_spec._unit = new_data.unit
else:
new_spec._unit = u.Unit(unit)

if self.uncertainty is not None:
new_spec.uncertainty = StdDevUncertainty(
self.uncertainty.represent_as(StdDevUncertainty).quantity.to(
unit, equivalencies=equivalencies))

new_spec._convert_flux(
unit, equivalencies=equivalencies, suppress_conversion=suppress_conversion)
return new_spec

@property
Expand Down Expand Up @@ -175,7 +179,7 @@ def velocity(self):

Returns
-------
~`astropy.units.Quantity`
new_data : `~astropy.units.Quantity`
The converted dispersion array in the new dispersion space.
"""
if self.rest_value is None:
Expand All @@ -202,8 +206,7 @@ def with_spectral_unit(self, unit, velocity_convention=None,
self.with_spectral_axis_unit(unit, velocity_convention=velocity_convention,
rest_value=rest_value)

def with_spectral_axis_unit(self, unit, velocity_convention=None,
rest_value=None):
def with_spectral_axis_unit(self, unit, velocity_convention=None, rest_value=None):
"""
Returns a new spectrum with a different spectral axis unit. Note that this creates a new
object using the converted spectral axis and thus drops the original WCS, if it existed,
Expand All @@ -230,11 +233,9 @@ def with_spectral_axis_unit(self, unit, velocity_convention=None,
even if your spectrum has air wavelength units

"""

velocity_convention = velocity_convention if velocity_convention is not None else self.velocity_convention # noqa
velocity_convention = velocity_convention if velocity_convention is not None else self.velocity_convention # noqa
rest_value = rest_value if rest_value is not None else self.rest_value
unit = self._new_wcs_argument_validation(unit, velocity_convention,
rest_value)
unit = self._new_wcs_argument_validation(unit, velocity_convention, rest_value)

# Store the original unit information and WCS for posterity
meta = deepcopy(self._meta)
Expand All @@ -252,6 +253,24 @@ def with_spectral_axis_unit(self, unit, velocity_convention=None,
return self.__class__(flux=self.flux, spectral_axis=new_spectral_axis, meta=meta,
uncertainty=self.uncertainty, mask=self.mask)

def with_spectral_axis_and_flux_units(self, spectral_axis_unit, flux_unit,
velocity_convention=None, rest_value=None,
flux_equivalencies=None, suppress_flux_conversion=False):
"""Perform :meth:`with_spectral_axis_unit` and :meth:`with_flux_unit` together.
See the respective methods for input and output definitions.

Returns
-------
new_spec : `~specutils.Spectrum1D`
Spectrum in requested units.

"""
new_spec = self.with_spectral_axis_unit(
spectral_axis_unit, velocity_convention=velocity_convention, rest_value=rest_value)
new_spec._convert_flux(
flux_unit, equivalencies=flux_equivalencies, suppress_conversion=suppress_flux_conversion)
return new_spec

def _new_wcs_argument_validation(self, unit, velocity_convention,
rest_value):
# Allow string specification of units, for example
Expand Down
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