Spectral Regions¶
A spectral region may be defined and may encompass one, or more,
sub-regions. They are independent of a Spectrum1D
object. There, one may define a spectral region and it may be used
on Spectrum1D objects of different dispersion
sampling.
Spectral regions can be defined either as a single region by passing
two Quantity’s or by passing a list of 2-tuples. By
definition the SpectralRegion will be ordered
based on the lower bound of each 2-tuple.
>>> from astropy import units as u
>>> from specutils.spectra import SpectralRegion
>>> sr = SpectralRegion(0.45*u.um, 0.6*u.um)
>>> sr_two = SpectralRegion([(0.45*u.um, 0.6*u.um), (0.8*u.um, 0.9*u.um)])
SpectralRegion can be combined by using the ‘+’ operator:
>>> from astropy import units as u
>>> from specutils.spectra import SpectralRegion
>>> sr = SpectralRegion(0.45*u.um, 0.6*u.um) + SpectralRegion(0.8*u.um, 0.9*u.um)
Regions can also be added in place:
>>> from astropy import units as u
>>> from specutils.spectra import SpectralRegion
>>> sr1 = SpectralRegion(0.45*u.um, 0.6*u.um)
>>> sr2 = SpectralRegion(0.8*u.um, 0.9*u.um)
>>> sr1 += sr2
Regions can be sliced by indexing by an integer or by a range:
>>> from astropy import units as u
>>> from specutils.spectra import SpectralRegion
>>> sr = SpectralRegion(0.15*u.um, 0.2*u.um) + SpectralRegion(0.3*u.um, 0.4*u.um) +\
... SpectralRegion(0.45*u.um, 0.6*u.um) + SpectralRegion(0.8*u.um, 0.9*u.um) +\
... SpectralRegion(1.0*u.um, 1.2*u.um) + SpectralRegion(1.3*u.um, 1.5*u.um)
>>> # Get on spectral region (returns a SpectralRegion instance)
>>> sone = sr1[0]
>>> # Slice spectral region.
>>> subsr = sr[3:5]
>>> # SpectralRegion: 0.8 um - 0.9 um, 1.0 um - 1.2 um
The lower and upper bounds on a region are accessed by calling lower
or upper. The lower bound of a SpectralRegion is the
minimum of the lower bounds of each sub-region and the upper bound is the
maximum of the upper bounds:
>>> from astropy import units as u
>>> from specutils.spectra import SpectralRegion
>>> sr = SpectralRegion(0.15*u.um, 0.2*u.um) + SpectralRegion(0.3*u.um, 0.4*u.um) +\
... SpectralRegion(0.45*u.um, 0.6*u.um) + SpectralRegion(0.8*u.um, 0.9*u.um) +\
... SpectralRegion(1.0*u.um, 1.2*u.um) + SpectralRegion(1.3*u.um, 1.5*u.um)
>>> # Bounds on the spectral region (most minimum and maximum bound)
>>> print(sr.bounds)
(<Quantity 0.15 um>, <Quantity 1.5 um>)
>>> # Lower bound on the spectral region (most minimum)
>>> sr.lower
<Quantity 0.15 um>
>>> sr.upper
<Quantity 1.5 um>
>>> # Lower bound on one element of the spectral region.
>>> sr[3].lower
<Quantity 0.8 um>
One can also delete a sub-region: .. code-block:: python
>>> from astropy import units as u
>>> from specutils.spectra import SpectralRegion
>>> sr = SpectralRegion(0.15*u.um, 0.2*u.um) + SpectralRegion(0.3*u.um, 0.4*u.um) +\
... SpectralRegion(0.45*u.um, 0.6*u.um) + SpectralRegion(0.8*u.um, 0.9*u.um) +\
... SpectralRegion(1.0*u.um, 1.2*u.um) + SpectralRegion(1.3*u.um, 1.5*u.um)
>>> del sr[1]
>>> sr
[(<Quantity 0.15 um>, <Quantity 0.2 um>),
(<Quantity 0.45 um>, <Quantity 0.6 um>),
(<Quantity 0.8 um>, <Quantity 0.9 um>),
(<Quantity 1. um>, <Quantity 1.2 um>),
(<Quantity 1.3 um>, <Quantity 1.5 um>)]
There is also the ability to iterate:
>>> from astropy import units as u
>>> from specutils.spectra import SpectralRegion
>>> sr = SpectralRegion(0.15*u.um, 0.2*u.um) + SpectralRegion(0.3*u.um, 0.4*u.um) +\
... SpectralRegion(0.45*u.um, 0.6*u.um) + SpectralRegion(0.8*u.um, 0.9*u.um) +\
... SpectralRegion(1.0*u.um, 1.2*u.um) + SpectralRegion(1.3*u.um, 1.5*u.um)
>>> for s in sr:
... print(s.lower)
SpectralRegion: 0.15 um - 0.2 um
SpectralRegion: 0.3 um - 0.4 um
SpectralRegion: 0.45 um - 0.6 um
SpectralRegion: 0.8 um - 0.9 um
SpectralRegion: 1.0 um - 1.2 um
SpectralRegion: 1.3 um - 1.5 um
And, lastly, there is the ability to invert a SpectralRegion given a
lower and upper bound. For example, if a set of ranges are defined each defining a range
around lines, then calling invert will return a SpectralRegion that
defines the baseline/noise regions:
>>> from astropy import units as u
>>> from specutils.spectra import SpectralRegion
>>> sr = SpectralRegion(0.15*u.um, 0.2*u.um) + SpectralRegion(0.3*u.um, 0.4*u.um) +\
... SpectralRegion(0.45*u.um, 0.6*u.um) + SpectralRegion(0.8*u.um, 0.9*u.um) +\
... SpectralRegion(1.0*u.um, 1.2*u.um) + SpectralRegion(1.3*u.um, 1.5*u.um)
>>> sr_inverted = sr.invert(0.05*u.um, 3*u.um)
>>> sr_inverted
SpectralRegion: 0.05 um - 0.15 um, 0.2 um - 0.3 um, 0.4 um - 0.45 um, 0.6 um - 0.8 um, 0.9 um - 1.0 um, 1.2 um - 1 .3 um, 1.5 um - 3.0 um
Region Extraction¶
Given a SpectralRegion, one can extract a sub-spectrum
from a Spectrum1D object. If the SpectralRegion
has multiple sub-regions then a list of Spectrum1D objects will
be returned.
An example of a single sub-region SpectralRegion:
>>> from astropy import units as u
>>> import numpy as np
>>> from specutils import Spectrum1D, SpectralRegion
>>> from specutils.manipulation import extract_region
>>> region = SpectralRegion(8*u.nm, 22*u.nm)
>>> spectrum = Spectrum1D(spectral_axis=np.arange(1, 50) * u.nm, flux=np.random.sample(49)*u.Jy)
>>> sub_spectrum = extract_region(spectrum, region)
>>> sub_spectrum.spectral_axis
<Quantity [ 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20.,
21., 22.] nm>
An example of a multiple sub-region SpectralRegion:
>>> from astropy import units as u
>>> import numpy as np
>>> from specutils import Spectrum1D, SpectralRegion
>>> from specutils.manipulation import extract_region
>>> region = SpectralRegion([(8*u.nm, 22*u.nm), (34*u.nm, 40*u.nm)])
>>> spectrum = Spectrum1D(spectral_axis=np.arange(1, 50) * u.nm, flux=np.random.sample(49)*u.Jy)
>>> sub_spectra = extract_region(spectrum, region)
>>> sub_spectra[0].spectral_axis
<Quantity [ 8., 9., 10., 11., 12., 13., 14., 15., 16., 17., 18., 19., 20.,
21., 22.] nm>
>>> sub_spectra[1].spectral_axis
<Quantity [34., 35., 36., 37., 38., 39., 40.] nm>
Reference/API¶
Classes¶
SpectralRegion(*args) |
A SpectralRegion is a container class enables some simplicty in defining and passing a region (interval) for a spectrum. |