SpectralRegion

class specutils.SpectralRegion(*args)

Bases: object

A SpectralRegion is a container class for regions (intervals) along a spectral coordinate.

This class can either represent a single contiguous region or a set of regions related to each other in some way (For example, a pair of continuum windows around a line or a doublet of lines).

Parameters:

*argsvariable

Either a single parameter or two parameters can be given:

• 1 argument regioniter: An iterable of length-2 Quantity objects (or a single n x 2 Quantity object), where the length-2 dimension is lower, upper.

• lower, upper: Each should be an Quantity object.

Notes

The subregions will be ordered based on the lower bound of each subregion.

Attributes Summary

bounds	Compute the lower and upper extent of the SpectralRegion.
lower	The most minimum value of the sub-regions.
subregions	An iterable over (lower, upper) tuples that are each of the sub-regions.
upper	The most maximum value of the sub-regions.

Methods Summary

as_table()	Returns an QTable with the upper and lower bound of each subregion in the SpectralRegion.
contains(spectral_value)	Determine whether a spectral axis value is within the defined spectral region.
from_center([center, width])	SpectralRegion class method that enables the definition of a SpectralRegion from the center and width rather than lower and upper bounds.
from_line_list(table[, width])	Generate a SpectralRegion instance from the QTable object returned from find_lines_derivative or find_lines_threshold.
from_qtable(table)	Generate a SpectralRegion instance from an QTable object has has lower_bound and upper_bound columns
intersection(other)	Return a region representing the intersection of this region with other.
invert(lower_bound, upper_bound)	Invert this spectral region.
invert_from_spectrum(spectrum)	Invert a SpectralRegion based on the extent of the input spectrum.
read(filename)	Create a SpectralRegion from an ecsv file output by the SpectralRegion.write method.
symmetric_difference(other)	Return the union of the two regions minus any areas contained in the intersection of the two regions.
to_subregions()	Dummy method to allow simpler recursion in CompoundSpectralRegion
union(other)	Return a region representing the union of this region with other.
write([filename, overwrite])	Write the SpectralRegion to an ecsv file using QTable.

Attributes Documentation

bounds

Compute the lower and upper extent of the SpectralRegion.

lower

The most minimum value of the sub-regions.

The sub-regions are ordered based on the lower bound, so the lower bound for this instance is the lower bound of the first sub-region.

subregions

An iterable over (lower, upper) tuples that are each of the sub-regions.

upper

The most maximum value of the sub-regions.

The sub-regions are ordered based on the lower bound, but the upper bound might not be the upper bound of the last sub-region so we have to look for it.

Methods Documentation

as_table()

Returns an QTable with the upper and lower bound of each subregion in the SpectralRegion.

contains(spectral_value)

Determine whether a spectral axis value is within the defined spectral region.

Parameters:

spectral_valueQuantity

The value (wavelength, frequency, etc) to check for inclusion in the SpectralRegion.

classmethod from_center(center=None, width=None)

SpectralRegion class method that enables the definition of a SpectralRegion from the center and width rather than lower and upper bounds.

Parameters:

centerScalar Quantity with pixel or any valid spectral_axis unit

The center of the spectral region.

widthScalar Quantity with pixel or any valid spectral_axis unit

The full width of the spectral region (upper bound - lower bound).

classmethod from_line_list(table, width=1)

Generate a SpectralRegion instance from the QTable object returned from find_lines_derivative or find_lines_threshold.

Parameters:

tableQTable

List of found lines.

widthfloat

The width of the spectral line region. If not unit information is provided, it’s assumed to be the same units as used in the line list table.

Returns:

SpectralRegion

The spectral region based on the line list.

classmethod from_qtable(table)

Generate a SpectralRegion instance from an QTable object has has lower_bound and upper_bound columns

Parameters:

tableQTable

An QTable object with lower_bound and upper_bound columns.

Returns:

SpectralRegion

The spectral region based on the table of bounds.

intersection(other)

Return a region representing the intersection of this region with other.

Parameters:

otherSpectralRegion

The other region to use for the intersection.

invert(lower_bound, upper_bound)

Invert this spectral region. That is, given a set of sub-regions this object defines, create a new SpectralRegion such that the sub-regions are defined in the new one as regions not in this SpectralRegion.

Parameters:

lower_boundQuantity

The lower bound of the region. Can be scalar with pixel or any valid spectral_axis unit that is equal to or compatible with the unit of lower_bound.

upper_boundQuantity

The upper bound of the region. Can be scalar with pixel or any valid spectral_axis unit that is equal to or compatible with the unit of lower_bound.

Returns:

spectral_regionSpectralRegion

Spectral region of the non-selected regions.

Raises:

ValueError

Raised when upper_bound and lower_bound do not have compatible units.

Notes

This is applicable if, for example, a SpectralRegion has sub-regions defined for peaks in a spectrum and then one wants to create a SpectralRegion defined as all the non-peaks, then one could use this function.

As an example, assume this SpectralRegion is defined as sr = SpectralRegion([(0.45*u.um, 0.6*u.um), (0.8*u.um, 0.9*u.um)]). If we call sr_invert = sr.invert(0.3*u.um, 1.0*u.um) then sr_invert will be SpectralRegion([(0.3*u.um, 0.45*u.um), (0.6*u.um, 0.8*u.um), (0.9*u.um, 1*u.um)])

invert_from_spectrum(spectrum)

Invert a SpectralRegion based on the extent of the input spectrum.

See notes in SpectralRegion.invert() method.

classmethod read(filename)

Create a SpectralRegion from an ecsv file output by the SpectralRegion.write method.

Parameters:

filenamestr

The name of the ecsv file on disk to be read in as a SpectralRegion.

symmetric_difference(other)

Return the union of the two regions minus any areas contained in the intersection of the two regions.

Parameters:

otherSpectralRegion

The other region to use for the symmetric difference.

to_subregions()

Dummy method to allow simpler recursion in CompoundSpectralRegion

union(other)

Return a region representing the union of this region with other.

Parameters:

otherSpectralRegion

The other region to use for the union.

write(filename='spectral_region.ecsv', overwrite=True)

Write the SpectralRegion to an ecsv file using QTable. Overwrites by default.