Read/write 1d spectrum from/to fits file¶
The routines read1dFitsSpec() and write1dFitsSpec()
provide simple interfaces for reading and writing one-dimensional fits
spectra with pyfits (astropy.io.fits).
Reading fits spectrum¶
- PyAstronomy.pyasl.read1dFitsSpec(fn, hdu=0, fullout=False, CRPIX1=None, keymap={})¶
Read a simple 1d spectrum from fits file.
Reads a 1d-spectrum from a file and constructs the associated wavelength axis. To this end, the expression: wvl = ((np.arange(N) + 1.0) - CRPIX1) * CDELT1 + CRVAL1 will be evaluated, where N is the number of bins and CRPIX1, CDELT1, and CRVAL1 are header keywords.
- Parameters
- fnstring
Filename
- hduint, optional
The number of the HDU to be used. The default is 0, i.e., the primary HDU.
- fulloutboolean, optional
If True, the header keywords used to construct the wavelength axis will be returned. The default is False.
- CRPIX1int, optional
Can be used to circumvent missing CRPIX1 entry.
- keymapdict, optional
Can be used to map header keywords
- Returns
- wvlarray
The wavelength array.
- flxarray
The flux array.
Examples
from PyAstronomy import pyasl wvl, flx = pyasl.read1dFitsSpec("mySpectrum.fits")
Writing fits spectrum¶
- PyAstronomy.pyasl.write1dFitsSpec(fn, flux, wvl=None, waveParams=None, fluxErr=None, header=None, clobber=False, refFileName=None, refFileExt=0)¶
Write a 1d spectrum with equidistant binning to a fits file.
Write a 1d-spectrum to a file. Wavelength axis and header keywords are related through the following expression: wvl = ((np.arange(N) + 1.0) - CRPIX1) * CDELT1 + CRVAL1, where CRPIX1, CDELT1, and CRVAL1 are the relevant header keywords.
The function allows to specify an existing fits extension, from which the header will be cloned. Alternatively, an arbitrary, user-defined header may be given.
- Parameters
- fnstring
Filename
- fluxarray
Flux array
- wvlarray, optional
Wavelength array. Either the wavelength array or the header keywords have to be provided (see waveParams).
- waveParamsdict, optional
Wavelength information required in the fits-header. Required keys are CDELT, CRVAL, CRPIX or (CDELT1, CRVAL1, CRPIX1).
- fluxErrarray, optional
Flux errors. If given, the error will be stored in an additional extension.
- headerdict, optional
Dictionary with header information to be transfered to the new file. Note that the wavelength information will be overwritten by the information given to this routine. If both, a reference file to clone the header from and the header parameters are given, the cloned header from the reference file will be overwritten and extended by the keywords specified here.
- refFileNamestring, optional
Clone header keywords from a reference file. Note that the wavelength information will be overwritten by the information by the information given to this routine.
- refFileExtint, optional
Reference-file extension to be used for cloning the header keywords. The default is 0.
Example of usage¶
import numpy as np
from PyAstronomy import pyasl
# Generate a "spectrum"
wvl = np.arange(5000., 5010., 0.01)
flux = np.random.normal(1.0, 0.01, wvl.size)
# Write spectrum providing wavelength array
pyasl.write1dFitsSpec("test1.fits", flux, wvl=wvl, clobber=True)
# Write spectrum specifying wavelength-related header keywords
# manually
wp = {"CRVAL1": 5000., "CDELT1": 0.01, "CRPIX1": 1}
pyasl.write1dFitsSpec("test2.fits", flux, waveParams=wp, clobber=True)
