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===================
Spectrum Arithmetic
===================
Specutils sports the ability to perform arithmetic operations over spectrum
data objects. There is full support for propagating unit information.
.. note:: Spectrum arithmetic requires that the two spectrum objects have
compatible WCS information.
.. warning:: Specutils does not currently implement interpolation techniques
for converting spectral axes information from one WCS source to
another.
Basic Arithmetic
----------------
Arithmetic support includes addition, subtract, multiplication, and division.
.. code-block:: python
>>> from specutils import Spectrum
>>> import astropy.units as u
>>> import numpy as np
>>> rng = np.random.default_rng(12345)
>>> spec1 = Spectrum(spectral_axis=np.arange(1, 50) * u.nm, flux=rng.random(49)*u.Jy)
>>> spec2 = Spectrum(spectral_axis=np.arange(1, 50) * u.nm, flux=rng.random(49)*u.Jy)
>>> spec3 = spec1 + spec2
>>> spec3 # doctest: +FLOAT_CMP
<Spectrum(flux=[0.8559405665668484 ... 0.9711264429515736] Jy (shape=(49,), mean=0.91592 Jy); spectral_axis=<SpectralAxis
(observer to target:
radial_velocity=0.0 km / s
redshift=0.0)
[ 1. 2. 3. ... 47. 48. 49.] nm> (length=49))>
Propagation of Uncertainties
----------------------------
Arithmetic operations also support the propagation of unceratinty information.
.. code-block:: python
>>> from astropy.nddata import StdDevUncertainty
>>> rng = np.random.default_rng(12345)
>>> wave = np.arange(10) * u.nm
>>> spec1 = Spectrum(spectral_axis=wave,
... flux=rng.random(10)*u.Jy,
... uncertainty=StdDevUncertainty(rng.random(10) * 0.1))
>>> spec2 = Spectrum(spectral_axis=wave,
... flux=rng.random(10)*u.Jy,
... uncertainty=StdDevUncertainty(rng.random(10) * 0.1))
>>> spec1.uncertainty
StdDevUncertainty([0.02482457, 0.09488812, 0.06672375, 0.00958979,
0.04418397, 0.08864799, 0.06974535, 0.03264729,
0.07339282, 0.0220135 ])
>>> spec2.uncertainty
StdDevUncertainty([0.08547419, 0.06016212, 0.09319884, 0.07247814,
0.08605513, 0.09293378, 0.0546186 , 0.0937673 ,
0.04949879, 0.02737732])
>>> spec3 = spec1 + spec2
>>> spec3.uncertainty
StdDevUncertainty([0.08900616, 0.11235317, 0.11462147, 0.07310981,
0.09673525, 0.12843346, 0.08858671, 0.09928822,
0.08852478, 0.03512992])
Reference/API
-------------
.. automodapi:: specutils.spectra.spectrum_mixin
:no-heading:
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