###############################
Extinguish or Unextinguish Data
###############################

Two of the three flavors of models include a function to calculate the
factor to multiple (extinguish) or divide (unextinguish) a spectrum by
to add or remove the effects of dust, respectively.

Extinguish is also often called reddening.  Extinguishing a spectrum often
reddens the flux, but sometimes 'bluens' the flux
(e.g, on the short wavelength side of the 2175 A bump).
So extinguish is the more generic term.

Extinguish a Blackbody
======================

.. plot::
   :include-source:

   import matplotlib.pyplot as plt
   from matplotlib.ticker import ScalarFormatter
   import numpy as np

   import astropy.units as u
   from astropy.modeling.models import BlackBody

   from dust_extinction.parameter_averages import G23

   # generate wavelengths between 0.092 and 31 microns
   #    within the valid range for the G23 R(V) dependent relationship
   lam = np.logspace(np.log10(0.092), np.log10(31.0), num=1000)

   # setup the inputs for the blackbody function
   wavelengths = lam*1e4*u.AA
   temperature = 10000*u.K

   # get the blackbody flux
   bb_lam = BlackBody(10000*u.K, scale=1.0 * u.erg / (u.cm ** 2 * u.AA * u.s * u.sr))
   flux = bb_lam(wavelengths)

   # initialize the model
   ext = G23(Rv=3.1)

   # get the extinguished blackbody flux for different amounts of dust
   flux_ext_av05 = flux*ext.extinguish(wavelengths, Av=0.5)
   flux_ext_av15 = flux*ext.extinguish(wavelengths, Av=1.5)
   flux_ext_ebv10 = flux*ext.extinguish(wavelengths, Ebv=1.0)

   # plot the intrinsic and extinguished fluxes
   fig, ax = plt.subplots()

   ax.plot(wavelengths, flux, label='Intrinsic')
   ax.plot(wavelengths, flux_ext_av05, label='$A(V) = 0.5$')
   ax.plot(wavelengths, flux_ext_av15, label='$A(V) = 1.5$')
   ax.plot(wavelengths, flux_ext_ebv10, label='$E(B-V) = 1.0$')

   ax.set_xlabel('$\lambda$ [$\AA$]')
   ax.set_ylabel('$Flux$')

   ax.set_xscale('log')
   ax.xaxis.set_major_formatter(ScalarFormatter())
   ax.set_yscale('log')

   ax.set_title('Example extinguishing a blackbody')

   ax.legend(loc='best')
   plt.tight_layout()
   plt.show()

Notebooks
=========

A great way to show how to use the `dust_extinction` package is using a
jupyter notebook.  Check out the
`Analyzing interstellar reddening and calculating synthetic photometry
<http://learn.astropy.org/tutorials/color-excess.html>`_
notebook that was created as part of the
`Learn.Astropy
<http://learn.astropy.org/>`_ effort.