Source code for specutils.fitting.continuum
import astropy.units as u
from astropy.modeling.polynomial import Chebyshev1D
from astropy.modeling.fitting import LevMarLSQFitter
from ..fitting import fit_lines
from ..manipulation.smoothing import median_smooth
from ..spectra import SpectralRegion
__all__ = ['fit_continuum', 'fit_generic_continuum']
[docs]
def fit_generic_continuum(spectrum, median_window=3, model=Chebyshev1D(3),
fitter=LevMarLSQFitter(),
exclude_regions=None, weights=None):
"""
Basic fitting of the continuum of an input spectrum. The input
spectrum is smoothed using a median filter to remove the spikes.
Parameters
----------
spectrum : Spectrum1D
The spectrum object overwhich the equivalent width will be calculated.
model : list of `~astropy.modeling.Model`
The list of models that contain the initial guess.
median_window : float
The width of the median smoothing kernel used to filter the data before
fitting the continuum. See the ``kernel_size`` parameter of
`~scipy.signal.medfilt` for more information.
fitter : `~astropy.fitting._FitterMeta`
The astropy fitter to use for fitting the model.
Default: `~astropy.modeling.fitting.LevMarLSQFitter`
exclude_regions : list of 2-tuples
List of regions to exclude in the fitting. Passed through
to the fitmodels routine.
weights : list (NOT IMPLEMENTED YET)
List of weights to define importance of fitting regions.
Returns
-------
continuum_model
Fitted continuum as a model of whatever class ``model`` provides.
Notes
-----
* Could add functionality to set the bounds in
``model`` if they are not set.
* The models in the list of ``model`` are added together and passed as a
compound model to the `~astropy.modeling.fitting.Fitter` class instance.
"""
# Simple median smooth to remove spikes and peaks
spectrum_smoothed = median_smooth(spectrum, median_window)
return fit_continuum(spectrum_smoothed, model=model, fitter=fitter,
exclude_regions=exclude_regions, weights=weights)
[docs]
def fit_continuum(spectrum, model=Chebyshev1D(3), fitter=LevMarLSQFitter(),
exclude_regions=None, window=None, weights=None):
"""
Entry point for fitting using the `~astropy.modeling.fitting`
machinery.
Parameters
----------
spectrum : Spectrum1D
The spectrum object overwhich the equivalent width will be calculated.
model: list of `~astropy.modeling.Model`
The list of models that contain the initial guess.
fitter : `~astropy.fitting._FitterMeta`
The astropy fitter to use for fitting the model.
Default: `~astropy.modeling.fitting.LevMarLSQFitter`
exclude_regions : list of 2-tuples
List of regions to exclude in the fitting. Passed through
to the fitmodels routine.
window : tuple of wavelengths
Start and end wavelengths used for fitting.
weights : list (NOT IMPLEMENTED YET)
List of weights to define importance of fitting regions.
Returns
-------
models : list of `~astropy.modeling.Model`
The list of models that contain the fitted model parameters.
"""
if weights is not None:
raise NotImplementedError("Weights support is not yet implemented.")
w = window
if type(w) in [list, tuple] and all([_is_valid_sequence(x) for x in w]):
w = SpectralRegion(w)
# Fit the flux to the model
continuum_spectrum = fit_lines(spectrum, model, fitter, exclude_regions,
weights, w)
return continuum_spectrum
# Checks for sequences of of 2-tuples with Quantities
def _is_valid_sequence(value):
if type(value) in [list, tuple]:
return len(value) == 2 and \
isinstance(value[0], u.Quantity) and \
isinstance(value[1], u.Quantity)
return False