def flatspectrum(xarr, yarr, mode='mean', thresh=3, iter=5, order=3):
"""Remove the continuum from a spectrum either by masking it or fitting
and subtracting it.
xarr= input x-vales (pixels or wavelength)
yarr= flux or counts for the spectrum
mode=None--no subtraction
mean--subtract off the mean
poly--subtact off a fit
mask--return a spectra with continuum set to zero
"""
if mode == 'mean':
# subtract off the mean value
sarr = yarr - clipstats(yarr, thresh, iter)[0]
elif mode == 'poly':
# calculate the statistics and mask all of the mask with values above
# these
it = interfit(xarr, yarr, function='poly', order=order)
it.interfit()
sarr = yarr - it(xarr)
elif mode == 'mask':
# mask the values
mean, std = clipstats(yarr, thresh, iter)
mask = (yarr < mean + thresh * std)
sarr = yarr.copy()
sarr[mask] = 0
else:
sarr = yarr.copy()
return sarr
def flatspectrum(xarr, yarr, mode='mean', thresh=3, iter=5, order=3):
"""Remove the continuum from a spectrum either by masking it or fitting and subtracting it.
xarr= input x-vales (pixels or wavelength)
yarr= flux or counts for the spectrum
mode=None--no subtraction
mean--subtract off the mean
poly--subtact off a fit
mask--return a spectra with continuum set to zero
"""
if mode=='mean':
#subtract off the mean value
sarr=yarr-clipstats(yarr, thresh, iter)[0]
elif mode=='poly':
#calculate the statistics and mask all of the mask with values above these
it=interfit(xarr, yarr, function='poly', order=2)
it.interfit()
sarr=yarr-it(xarr)
elif mode=='mask':
#mask the values
mean, std = clipstats(yarr, thresh, iter)
mask=(yarr<mean+thresh*std)
sarr=yarr.copy()
sarr[mask]=0
else:
sarr=yarr.copy()
return sarr
def set_func(self):
if self.function in [
'poly', 'polynomial', 'spline', 'legendre', 'chebyshev']:
self.func = interfit(self.x_arr, self.w_arr,
function=self.function,
order=self.order, niter=self.niter,
thresh=self.thresh)
if self.function == 'model':
self.func = ModelSolution(self.x_arr, self.w_arr,
sgraph=self.sgraph, xlen=self.xlen,
yval=self.yval, order=self.order)
def set_func(self):
if self.function in [
'poly', 'polynomial', 'spline', 'legendre', 'chebyshev'
]:
self.func = interfit(self.x_arr,
self.w_arr,
function=self.function,
order=self.order,
niter=self.niter,
thresh=self.thresh)
if self.function == 'model':
self.func = ModelSolution(self.x_arr,
self.w_arr,
sgraph=self.sgraph,
xlen=self.xlen,
yval=self.yval,
order=self.order)
def bias(struct,subover=True,trim=True, subbias=False, bstruct=None,
median=False, function='polynomial',order=3,rej_lo=3,rej_hi=3,niter=10,
plotover=False, log=None, verbose=True):
"""Bias subtracts the bias levels from a frame. It will fit and subtract the overscan
region, trim the images, and subtract a master bias if required.
struct--image structure
subover--subtract the overscan region
trim--trim the image
subbias--subtract master bias
bstruct--master bias image structure
median--use the median instead of mean in image statistics
function--form to fit to the overscan region
order--order for the function
rej_lo--sigma of low points to reject in the fit
rej_hi--sigma of high points to reject in the fit
niter--number of iterations
log--saltio log for recording information
verbose--whether to print to stdout
"""
infile=saltkey.getimagename(struct[0])
# how many extensions?
nsciext = saltkey.get('NSCIEXT',struct[0])
nextend = saltkey.get('NEXTEND',struct[0])
nccd = saltkey.get('NCCDS',struct[0])
# how many amplifiers?--this is hard wired
amplifiers = 2 * nccd
#log the process
if subover and log:
message = '%28s %7s %5s %4s %6s' % \
('HDU','Overscan','Order','RMS','Niter')
log.message('\n --------------------------------------------------',
with_header=False, with_stdout=verbose)
log.message(message, with_header=False, with_stdout=verbose)
log.message(' --------------------------------------------------',
with_header=False, with_stdout=verbose)
if (plotover):
plt.figure(1)
plt.axes([0.1,0.1,0.8,0.8])
plt.xlabel('CCD Column')
plt.ylabel('Pixel Counts (e-)')
plt.ion()
#loop through the extensions and subtract the bias
for i in range(1,nsciext+1):
if struct[i].name=='SCI':
#get the bias section
biassec = saltkey.get('BIASSEC',struct[i])
y1,y2,x1,x2 = saltio.getSection(biassec, iraf_format=True)
#get the data section
datasec = saltkey.get('DATASEC',struct[i])
dy1,dy2, dx1, dx2 = saltio.getSection(datasec, iraf_format=True)
#setup the overscan region
if subover:
yarr=np.arange(y1,y2, dtype=float)
data=struct[i].data
odata=struct[i].data[y1:y2,x1:x2]
if median:
odata=np.median((struct[i].data[y1:y2,x1:x2]),axis=1)
olevel=np.median((struct[i].data[y1:y2,x1:x2]))
saltkey.new('OVERSCAN','%f' % (olevel),'Overscan median value', struct[i])
else:
odata=np.mean((struct[i].data[y1:y2,x1:x2]),axis=1)
olevel=np.mean((struct[i].data[y1:y2,x1:x2]))
saltkey.new('OVERSCAN','%f' % (olevel),'Overscan mean value', struct[i])
#fit the overscan region
ifit=saltfit.interfit(yarr, odata, function=function, \
order=order, thresh=rej_hi, niter=niter)
try:
ifit.interfit()
coeffs=ifit.coef
ofit=ifit(yarr)
omean, omed, osigma=saltstat.iterstat((odata-ofit), sig=3, niter=5)
except ValueError:
#catch the error if it is a zero array
ofit=np.array(yarr)*0.0
osigma=0.0
except TypeError:
#catch the error if it is a zero array
ofit=np.array(yarr)*0.0
osigma=0.0
#if it hasn't been already, convert image to
#double format
struct[i].data = 1.0 * struct[i].data
try:
struct[i].header.remove('BZERO')
struct[i].header.remove('BSCALE')
except:
pass
#subtract the overscan region
for j in range(len(struct[i].data[0])):
struct[i].data[y1:y2,j] -= ofit
#report the information
if log:
message = '%25s[%1d] %8.2f %3d %7.2f %3d' % \
(infile, i, olevel, order, osigma, niter)
log.message(message, with_stdout=verbose, with_header=False)
#add the statistics to the image header
saltkey.new('OVERRMS','%f' % (osigma),'Overscan RMS value', struct[i])
#update the variance frame
if saltkey.found('VAREXT', struct[i]):
vhdu=saltkey.get('VAREXT', struct[i])
try:
vdata=struct[vhdu].data
#The bias level should not be included in the noise from the signal
for j in range(len(struct[i].data[0])):
vdata[y1:y2,j] -= ofit
#add a bit to make sure that the minimum error is the rednoise
rdnoise= saltkey.get('RDNOISE',struct[i])
vdata[vdata<rdnoise**2]=rdnoise**2
struct[vhdu].data=vdata+osigma**2
except Exception, e:
msg='Cannot update the variance frame in %s[%i] because %s' % (infile, vhdu, e)
raise SaltError(msg)
#plot the overscan region
if plotover:
plt.plot(yarr, odata)
plt.plot(yarr, ofit)
#trim the data and update the headers
if trim:
struct[i].data=struct[i].data[dy1:dy2,dx1:dx2]
datasec = '[1:'+str(dx2-dx1)+',1:'+str(dy2-dy1)+']'
saltkey.put('DATASEC',datasec,struct[i])
#update the variance frame
if saltkey.found('VAREXT', struct[i]):
vhdu=saltkey.get('VAREXT', struct[i])
struct[vhdu].data=struct[vhdu].data[dy1:dy2,dx1:dx2]
datasec = '[1:'+str(dx2-dx1)+',1:'+str(dy2-dy1)+']'
saltkey.put('DATASEC',datasec,struct[vhdu])
#update the BPM frame
if saltkey.found('BPMEXT', struct[i]):
bhdu=saltkey.get('BPMEXT', struct[i])
struct[bhdu].data=struct[bhdu].data[dy1:dy2,dx1:dx2]
datasec = '[1:'+str(dx2-dx1)+',1:'+str(dy2-dy1)+']'
saltkey.put('DATASEC',datasec,struct[bhdu])
#subtract the master bias if necessary
if subbias and bstruct:
struct[i].data -= bstruct[i].data
#update the variance frame
if saltkey.found('VAREXT', struct[i]):
vhdu=saltkey.get('VAREXT', struct[i])
try:
vdata=struct[vhdu].data
struct[vhdu].data=vdata+bstruct[vhdu].data
except Exception, e:
msg='Cannot update the variance frame in %s[%i] because %s' % (infile, vhdu, e)
raise SaltError(msg)
def bias(struct,
subover=True,
trim=True,
subbias=False,
bstruct=None,
median=False,
function='polynomial',
order=3,
rej_lo=3,
rej_hi=3,
niter=10,
plotover=False,
log=None,
verbose=True):
"""Bias subtracts the bias levels from a frame. It will fit and subtract the overscan
region, trim the images, and subtract a master bias if required.
struct--image structure
subover--subtract the overscan region
trim--trim the image
subbias--subtract master bias
bstruct--master bias image structure
median--use the median instead of mean in image statistics
function--form to fit to the overscan region
order--order for the function
rej_lo--sigma of low points to reject in the fit
rej_hi--sigma of high points to reject in the fit
niter--number of iterations
log--saltio log for recording information
verbose--whether to print to stdout
"""
infile = saltkey.getimagename(struct[0])
# how many extensions?
nsciext = saltkey.get('NSCIEXT', struct[0])
nextend = saltkey.get('NEXTEND', struct[0])
nccd = saltkey.get('NCCDS', struct[0])
# how many amplifiers?--this is hard wired
amplifiers = 2 * nccd
#log the process
if subover and log:
message = '%28s %7s %5s %4s %6s' % \
('HDU','Overscan','Order','RMS','Niter')
log.message(
'\n --------------------------------------------------',
with_header=False,
with_stdout=verbose)
log.message(message, with_header=False, with_stdout=verbose)
log.message(' --------------------------------------------------',
with_header=False,
with_stdout=verbose)
if (plotover):
plt.figure(1)
plt.axes([0.1, 0.1, 0.8, 0.8])
plt.xlabel('CCD Column')
plt.ylabel('Pixel Counts (e-)')
plt.ion()
#loop through the extensions and subtract the bias
for i in range(1, nsciext + 1):
if struct[i].name == 'SCI':
#get the bias section
biassec = saltkey.get('BIASSEC', struct[i])
y1, y2, x1, x2 = saltio.getSection(biassec, iraf_format=True)
#get the data section
datasec = saltkey.get('DATASEC', struct[i])
dy1, dy2, dx1, dx2 = saltio.getSection(datasec, iraf_format=True)
#setup the overscan region
if subover:
yarr = np.arange(y1, y2, dtype=float)
data = struct[i].data
odata = struct[i].data[y1:y2, x1:x2]
if median:
odata = np.median((struct[i].data[y1:y2, x1:x2]), axis=1)
olevel = np.median((struct[i].data[y1:y2, x1:x2]))
saltkey.new('OVERSCAN', '%f' % (olevel),
'Overscan median value', struct[i])
else:
odata = np.mean((struct[i].data[y1:y2, x1:x2]), axis=1)
olevel = np.mean((struct[i].data[y1:y2, x1:x2]))
saltkey.new('OVERSCAN', '%f' % (olevel),
'Overscan mean value', struct[i])
#fit the overscan region
ifit=saltfit.interfit(yarr, odata, function=function, \
order=order, thresh=rej_hi, niter=niter)
try:
ifit.interfit()
coeffs = ifit.coef
ofit = ifit(yarr)
omean, omed, osigma = saltstat.iterstat((odata - ofit),
sig=3,
niter=5)
except ValueError:
#catch the error if it is a zero array
ofit = np.array(yarr) * 0.0
osigma = 0.0
except TypeError:
#catch the error if it is a zero array
ofit = np.array(yarr) * 0.0
osigma = 0.0
#if it hasn't been already, convert image to
#double format
struct[i].data = 1.0 * struct[i].data
try:
struct[i].header.remove('BZERO')
struct[i].header.remove('BSCALE')
except:
pass
#subtract the overscan region
for j in range(len(struct[i].data[0])):
struct[i].data[y1:y2, j] -= ofit
#report the information
if log:
message = '%25s[%1d] %8.2f %3d %7.2f %3d' % \
(infile, i, olevel, order, osigma, niter)
log.message(message,
with_stdout=verbose,
with_header=False)
#add the statistics to the image header
saltkey.new('OVERRMS', '%f' % (osigma), 'Overscan RMS value',
struct[i])
#update the variance frame
if saltkey.found('VAREXT', struct[i]):
vhdu = saltkey.get('VAREXT', struct[i])
try:
vdata = struct[vhdu].data
#The bias level should not be included in the noise from the signal
for j in range(len(struct[i].data[0])):
vdata[y1:y2, j] -= ofit
#add a bit to make sure that the minimum error is the rednoise
rdnoise = saltkey.get('RDNOISE', struct[i])
vdata[vdata < rdnoise**2] = rdnoise**2
struct[vhdu].data = vdata + osigma**2
except Exception, e:
msg = 'Cannot update the variance frame in %s[%i] because %s' % (
infile, vhdu, e)
raise SaltError(msg)
#plot the overscan region
if plotover:
plt.plot(yarr, odata)
plt.plot(yarr, ofit)
#trim the data and update the headers
if trim:
struct[i].data = struct[i].data[dy1:dy2, dx1:dx2]
datasec = '[1:' + str(dx2 - dx1) + ',1:' + str(dy2 - dy1) + ']'
saltkey.put('DATASEC', datasec, struct[i])
#update the variance frame
if saltkey.found('VAREXT', struct[i]):
vhdu = saltkey.get('VAREXT', struct[i])
struct[vhdu].data = struct[vhdu].data[dy1:dy2, dx1:dx2]
datasec = '[1:' + str(dx2 - dx1) + ',1:' + str(dy2 -
dy1) + ']'
saltkey.put('DATASEC', datasec, struct[vhdu])
#update the BPM frame
if saltkey.found('BPMEXT', struct[i]):
bhdu = saltkey.get('BPMEXT', struct[i])
struct[bhdu].data = struct[bhdu].data[dy1:dy2, dx1:dx2]
datasec = '[1:' + str(dx2 - dx1) + ',1:' + str(dy2 -
dy1) + ']'
saltkey.put('DATASEC', datasec, struct[bhdu])
#subtract the master bias if necessary
if subbias and bstruct:
struct[i].data -= bstruct[i].data
#update the variance frame
if saltkey.found('VAREXT', struct[i]):
vhdu = saltkey.get('VAREXT', struct[i])
try:
vdata = struct[vhdu].data
struct[vhdu].data = vdata + bstruct[vhdu].data
except Exception, e:
msg = 'Cannot update the variance frame in %s[%i] because %s' % (
infile, vhdu, e)
raise SaltError(msg)
def fitradius(radius, data):
"""Fit a line to the data"""
it=interfit(radius, data, function='polynomial', order=3)
it.interfit()
d=it(radius)
return radius[d.argmax()]
def specsens(specfile, outfile, stdfile, extfile, airmass=None, exptime=None,
stdzp=3.68e-20, function='polynomial', order=3, thresh=3, niter=5,
fitter='gaussian', clobber=True, logfile='salt.log', verbose=True):
with logging(logfile, debug) as log:
# read in the specfile and create a spectrum object
obs_spectra = st.readspectrum(specfile.strip(), error=True, ftype='ascii')
# smooth the observed spectrum
# read in the std file and convert from magnitudes to fnu
# then convert it to fwave (ergs/s/cm2/A)
std_spectra = st.readspectrum(stdfile.strip(), error=False, ftype='ascii')
std_spectra.flux = Spectrum.magtoflux(std_spectra.flux, stdzp)
std_spectra.flux = Spectrum.fnutofwave(
std_spectra.wavelength, std_spectra.flux)
# Get the typical bandpass of the standard star,
std_bandpass = np.diff(std_spectra.wavelength).mean()
# Smooth the observed spectrum to that bandpass
obs_spectra.flux = st.boxcar_smooth(obs_spectra, std_bandpass)
# read in the extinction file (leave in magnitudes)
ext_spectra = st.readspectrum(extfile.strip(), error=False, ftype='ascii')
# determine the airmass if not specified
if saltio.checkfornone(airmass) is None:
message = 'Airmass was not supplied'
raise SALTSpecError(message)
# determine the exptime if not specified
if saltio.checkfornone(exptime) is None:
message = 'Exposure Time was not supplied'
raise SALTSpecError(message)
# calculate the calibrated spectra
log.message('Calculating the calibration curve for %s' % specfile)
cal_spectra = sensfunc(
obs_spectra, std_spectra, ext_spectra, airmass, exptime)
# plot(cal_spectra.wavelength, cal_spectra.flux * std_spectra.flux)
# fit the spectra--first take a first cut of the spectra
# using the median absolute deviation to throw away bad points
cmed = np.median(cal_spectra.flux)
cmad = saltstat.mad(cal_spectra.flux)
mask = (abs(cal_spectra.flux - cmed) < thresh * cmad)
mask = np.logical_and(mask, (cal_spectra.flux > 0))
# now fit the data
# Fit using a gaussian process.
if fitter=='gaussian':
from sklearn.gaussian_process import GaussianProcess
#Instanciate a Gaussian Process model
dy = obs_spectra.var[mask] ** 0.5
dy /= obs_spectra.flux[mask] / cal_spectra.flux[mask]
y = cal_spectra.flux[mask]
gp = GaussianProcess(corr='squared_exponential', theta0=1e-2,
thetaL=1e-4, thetaU=0.1, nugget=(dy / y) ** 2.0)
X = np.atleast_2d(cal_spectra.wavelength[mask]).T
# Fit to data using Maximum Likelihood Estimation of the parameters
gp.fit(X, y)
x = np.atleast_2d(cal_spectra.wavelength).T
# Make the prediction on the meshed x-axis (ask for MSE as well)
y_pred = gp.predict(x)
cal_spectra.flux = y_pred
else:
fit=interfit(cal_spectra.wavelength[mask], cal_spectra.flux[mask], function=function, order=order, thresh=thresh, niter=niter)
fit.interfit()
cal_spectra.flux=fit(cal_spectra.wavelength)
# write the spectra out
st.writespectrum(cal_spectra, outfile, ftype='ascii')
def specsens(specfile,
outfile,
stdfile,
extfile,
airmass=None,
exptime=None,
stdzp=3.68e-20,
function='polynomial',
order=3,
thresh=3,
niter=5,
fitter='gaussian',
clobber=True,
logfile='salt.log',
verbose=True):
with logging(logfile, debug) as log:
# read in the specfile and create a spectrum object
obs_spectra = st.readspectrum(specfile.strip(),
error=True,
ftype='ascii')
# smooth the observed spectrum
# read in the std file and convert from magnitudes to fnu
# then convert it to fwave (ergs/s/cm2/A)
std_spectra = st.readspectrum(stdfile.strip(),
error=False,
ftype='ascii')
std_spectra.flux = Spectrum.magtoflux(std_spectra.flux, stdzp)
std_spectra.flux = Spectrum.fnutofwave(std_spectra.wavelength,
std_spectra.flux)
# Get the typical bandpass of the standard star,
std_bandpass = np.diff(std_spectra.wavelength).mean()
# Smooth the observed spectrum to that bandpass
obs_spectra.flux = st.boxcar_smooth(obs_spectra, std_bandpass)
# read in the extinction file (leave in magnitudes)
ext_spectra = st.readspectrum(extfile.strip(),
error=False,
ftype='ascii')
# determine the airmass if not specified
if saltio.checkfornone(airmass) is None:
message = 'Airmass was not supplied'
raise SALTSpecError(message)
# determine the exptime if not specified
if saltio.checkfornone(exptime) is None:
message = 'Exposure Time was not supplied'
raise SALTSpecError(message)
# calculate the calibrated spectra
log.message('Calculating the calibration curve for %s' % specfile)
cal_spectra = sensfunc(obs_spectra, std_spectra, ext_spectra, airmass,
exptime)
# plot(cal_spectra.wavelength, cal_spectra.flux * std_spectra.flux)
# fit the spectra--first take a first cut of the spectra
# using the median absolute deviation to throw away bad points
cmed = np.median(cal_spectra.flux)
cmad = saltstat.mad(cal_spectra.flux)
mask = (abs(cal_spectra.flux - cmed) < thresh * cmad)
mask = np.logical_and(mask, (cal_spectra.flux > 0))
# now fit the data
# Fit using a gaussian process.
if fitter == 'gaussian':
from sklearn.gaussian_process import GaussianProcess
#Instanciate a Gaussian Process model
dy = obs_spectra.var[mask]**0.5
dy /= obs_spectra.flux[mask] / cal_spectra.flux[mask]
y = cal_spectra.flux[mask]
gp = GaussianProcess(corr='squared_exponential',
theta0=1e-2,
thetaL=1e-4,
thetaU=0.1,
nugget=(dy / y)**2.0)
X = np.atleast_2d(cal_spectra.wavelength[mask]).T
# Fit to data using Maximum Likelihood Estimation of the parameters
gp.fit(X, y)
x = np.atleast_2d(cal_spectra.wavelength).T
# Make the prediction on the meshed x-axis (ask for MSE as well)
y_pred = gp.predict(x)
cal_spectra.flux = y_pred
else:
fit = interfit(cal_spectra.wavelength[mask],
cal_spectra.flux[mask],
function=function,
order=order,
thresh=thresh,
niter=niter)
fit.interfit()
cal_spectra.flux = fit(cal_spectra.wavelength)
# write the spectra out
st.writespectrum(cal_spectra, outfile, ftype='ascii')
def fitradius(radius, data):
"""Fit a line to the data"""
it = interfit(radius, data, function='polynomial', order=3)
it.interfit()
d = it(radius)
return radius[d.argmax()]