PyAtomDB Example Scripts

These are examples of using the pyatomdb module in your projects. They can all be found in the examples subdirectory of the pyatomdb tarball.

Initial installation

import pyatomdb

This script shows the commands you should run when you first download pyatomdb.

It is recommended that you choose the location you want to install the
AtomDB data files (not the same as the python module) and set your
ATOMDB environment variable to point to it.




# call the setup routine

# this routine downloads a bunch of files and sets things up for you. It will 
# take a few minutes, depending on your internet connection.

print "Install complete!"

#and that's it!

# If you want to switch versions of atomdb (in this case to 3.0.2) later, call:
# pyatomdb.util.switch_version('3.0.2')

Make Line List

List the strongest lines in a given temperature and wavelength region:

import pyatomdb

This code will produce a list of lines in a given wavelength range at a
given temperature. It also shows the use of an NEI version, where you 
have to additionally specify the initial ionization temperature (or the
ionization fraction directly) and the elapsed Ne*t.

The results of the list_lines codes are numpy arrays which can be sorted any
way you wish. You can, of course, extract the lines easily at this point. There
is also a print_lines routine for a fixed format output.




# Adam Foster 2015-12-02
# version 0.1

#specify wavelength range, in Angstroms
wl = [8.0,9.0]

# electron temperature in K
Te = 1e7

# get equilibrium line list

res = pyatomdb.spectrum.list_lines(wl,Te=Te, teunit='K', minepsilon=1e-18)

# reprocess lines for printing
print "Unsorted line list:"

# re-sort lines, for a giggle
# for more information, look up numpy.sort: res is a numpy array.

print "sorted by Emissivity:"

# re-sort by element, ion then emissivity
print "sorted by Element, Ion, Emissivity:"

# now do an NEI version. This is slow at the moment, but functional.
Te_init = 1e4
tau = 1e11
res_nei = pyatomdb.spectrum.list_nei_lines(wl,Te=Te, teunit='K', \
                                           tau = tau)
print "NEI linelist (this takes a while):"

Get PI Cross Sections

Extract the PI cross section data:

import pyatomdb, numpy,os, pylab
  import as pyfits
  import pyfits

# This is a sample routine that reads in the photoionization data
# It also demonstrates using get_data, which should download the data you 
# need automagically from the AtomDB site.
# It also shows how to get the raw XSTAR PI cross sections. 

# going to get PI cross section from iron 16+ to 17+ (Fe XVII-XVIII)
Z = 26
z1 = 17

# get the AtomDB level data
lvdata = pyatomdb.atomdb.get_data(Z, z1, 'LV')

# get the XSTAR PI data from AtomDB
pidata = pyatomdb.atomdb.get_data(Z, z1, 'PI')

# set up the figure
fig = pylab.figure()
ax = fig.add_subplot(111)

# to calculate the cross section (in cm^2) at a given single energy E (in keV)
# does not currently work with vector input, so have to call in a loop if you 
# want multiple energies [I will fix this]

E = 10.

# get the ground level (the 0th entry in LV file) data
lvd = lvdata[1].data[0]

# This is the syntax for calculating the PI cross section of a given line
# This will work for non XSTAR data too.
sigma = pyatomdb.atomdb.sigma_photoion(E, Z, z1,lvd['phot_type'], lvd['phot_par'], \
               xstardata=pidata, xstarfinallev=1)

# To get the raw XSTAR cross sections (units: energy = keV, cross sections = Mb)               
# for level 1 -> 1 (ground to ground)
pixsec = pyatomdb.atomdb.sort_pi_data(pidata, 1,1)
ax.loglog(pixsec['energy'], pixsec['pi_param']*1e-18, label='raw xstar data')

# label the plot
ax.set_title('Plotting raw XSTAR PI cross sections. Fe XVII gnd to Fe XVIII gnd')
ax.set_xlabel("Energy (keV)")
ax.set_ylabel("PI cross section (cm$^{2}$)")

zzz=raw_input('press enter to continue')

Make a Spectrum

Make a broadened and unbroadened spectrum:

import pyatomdb, numpy, pylab

# set up a grid of energy bins to model the spectrum on:

# define a broadening, in keV, for the lines
de = 0.01

# define the temperature at which to plot (keV)
te = 3.0

# find the index which is closest to this temperature
ite = pyatomdb.spectrum.get_index( te, teunits='keV', logscale=False)

# create both a broadened and an unbroadened spectrum
a = pyatomdb.spectrum.make_spectrum(ebins, ite,dummyfirst=True)
b = pyatomdb.spectrum.make_spectrum(ebins, ite, broadening=de, \
# The dummyfirst argument adds an extra 0 at teh beginning of the
# returned array so it is the same length as ebins. It allows
# accurate plotting using the "drawstyle='steps'" flag to plot.

# plot the results
fig = pylab.figure()
ax = fig.add_subplot(111)

ax.loglog(ebins, a, drawstyle='steps', label='Unbroadened')
ax.loglog(ebins, b, drawstyle='steps', label='sigma = %.2f'%(de))
ax.set_xlabel('Energy (keV)')
ax.set_ylabel('Emissivity (ph cm$^{3}$ s$^{-1}$ bin$^{-1}$)')
zzz = raw_input("Press enter to continue")

print "Listing lines between 1 and 2 A"
# now list the lines in a wavelength region
llist = pyatomdb.spectrum.list_lines([1,2.0], index=ite)
# print these to screen
# print to screen, listing the energy, not the wavelength
print "Listing lines between 1 and 2 A, using keV."

pyatomdb.spectrum.print_lines(llist, specunits = 'keV')

Make a Spectrum version 2.0

Make a spectrum using the new Session class: This is significantly faster if you need to make lots of spectra (fitting, interpolating between 2 temperatures etc). Note the example requires an RMF and ARF file - adjust to fit your available response.

import pyatomdb, pylab, numpy, time

rmf = '/export1/projects/atomdb_308/hitomi/resp_100041010sxs.rmf'
arf = '/export1/projects/atomdb_308/hitomi/arf_100041010sxs.arf'

# create a session object. This contains the apec files, response files,
# and any previously calculated spectrs so that simple multiplication
# can be used to get the results without recalculating everything from scratch

data = pyatomdb.spectrum.Session()

# If you want to specify custom energy bins:
#ebins = numpy.linspace(1,2,1001)
#data.set_specbins(ebins, units='A')

# alternative method: just load the response and use its binning. Note
# that this will always be in keV currently, because reasons.

data.set_response(rmf, arf=arf)
ebins = data.ebins_response

# now get the spectrum at 4keV. This calculates (and stores) the 
# spectrum at each temperature nearby (~3.7, 4.3 keV)
# then linearly interpolates between the result
# vector is stored for each element at each temperature
# so if you change temperature/abundance, it's a simple multiplication adn
# interpolation instead of a total recalculation

t0 = time.time()
s=data.return_spectra(4.0, teunit='keV')
t1 = time.time()
# let's change the abundance

# and see how fast this goes this time, changing temperature and abund
s2=data.return_spectra(4.1, teunit='keV')
t2 = time.time()

print "first spectrum took %g seconds" %(t1-t0)
print "second spectrum took %g seconds" %(t2-t1)
print "note how much faster the second one was as I didn't recalculate everything from scratch!"

#linedata ='/export1/atomdb_latest/apec_v3.0.8_line.fits')

#spec = speclo*rlo + specup*rup

# some plotting of things

fig = pylab.figure()
ax = fig.add_subplot(111)
#ax2 = fig.add_subplot(212, sharex=ax)
s = numpy.append(0,s)
s += 1e-40

s2 = numpy.append(0,s2)
s2 += 1e-40
#spec = numpy.append(0,spec)
#spec += 1e-40

ax.plot(ebins, s, drawstyle='steps')
ax.plot(ebins, s2, drawstyle='steps')
#ax.plot(elo, spec, drawstyle='steps')

#ax2.plot(elo, s/spec, drawstyle='steps')

zzz=raw_input('Press enter to exit')