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.
>>> from specutils import Spectrum1D
>>> import astropy.units as u
>>> import numpy as np
>>> spec1 = Spectrum1D(spectral_axis=np.arange(1, 50) * u.nm, flux=np.random.sample(49)*u.Jy)
>>> spec2 = Spectrum1D(spectral_axis=np.arange(1, 50) * u.nm, flux=np.random.sample(49)*u.Jy)
>>> spec3 = spec1 + spec2
>>> spec3
Spectrum1D([1.42980955, 0.76450583, 0.53973912, 1.12714653, 1.46747729,
0.98485104, 1.13618017, 1.02447445, 0.68610084, 0.85083215,
0.57521794, 1.16854341, 1.05139223, 1.44550638, 1.67533841,
1.41277807, 0.46008942, 1.1399328 , 0.41708163, 0.61282024,
0.40034388, 0.95204057, 0.98280167, 1.30647318, 1.43317265,
0.71426198, 0.58622459, 1.17063336, 1.37244261, 1.06886942,
1.54349149, 1.15019089, 0.51719866, 1.23114699, 1.16464384,
0.90833751, 1.04018595, 1.34931354, 1.01936352, 0.39543304,
1.22407522, 0.34658842, 1.18760707, 1.38161461, 1.05829078,
1.57852604, 1.13365571, 0.59304282, 1.3913748 ])
>>> spec3.wavelength
<Quantity [ 10., 20., 30., 40., 50., 60., 70., 80., 90., 100.,
110., 120., 130., 140., 150., 160., 170., 180., 190., 200.,
210., 220., 230., 240., 250., 260., 270., 280., 290., 300.,
310., 320., 330., 340., 350., 360., 370., 380., 390., 400.,
410., 420., 430., 440., 450., 460., 470., 480., 490.] Angstrom>
Propagation of Uncertainties¶
Arithmetic operations also support the propagation of unceratinty information.
>>> from astropy.nddata import StdDevUncertainty
>>> spec1 = Spectrum1D(spectral_axis=np.arange(10) * u.nm, flux=np.random.sample(10)*u.Jy, uncertainty=StdDevUncertainty(np.random.sample(10) * 0.1))
>>> spec2 = Spectrum1D(spectral_axis=np.arange(10) * u.nm, flux=np.random.sample(10)*u.Jy, uncertainty=StdDevUncertainty(np.random.sample(10) * 0.1))
>>> spec1.uncertainty
StdDevUncertainty([0.04386832, 0.09909487, 0.07589192, 0.0311604 ,
0.07973579, 0.04687858, 0.01161918, 0.06013496,
0.00476118, 0.06720447])
>>> spec2.uncertainty
StdDevUncertainty([0.00889175, 0.00890437, 0.05194229, 0.08794455,
0.09918037, 0.04815417, 0.06464564, 0.0164324 ,
0.04358771, 0.08260218])
>>> spec3 = spec1 + spec2
>>> spec3.uncertainty
StdDevUncertainty([0.04476039, 0.09949412, 0.09196513, 0.09330174,
0.12725778, 0.06720435, 0.06568154, 0.06233969,
0.04384698, 0.10648737])