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casa
$Rev:20696$
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casa
$Rev:20696$
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Functions | |
| def | sdfit |
| def sdfit.sdfit | ( | infile = '', |
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antenna = 0, |
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fluxunit = '', |
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telescopeparm = '', |
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specunit = '', |
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restfreq = '', |
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frame = '', |
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doppler = '', |
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scanlist = [], |
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field = '', |
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iflist = [], |
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pollist = [], |
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fitfunc = 'gauss', |
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fitmode = 'auto', |
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maskline = [], |
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invertmask = False, |
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nfit = [], |
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thresh = 5.0, |
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min_nchan = 3, |
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avg_limit = 4, |
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box_size = 0.2, |
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edge = [0], |
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outfile = '', |
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overwrite = False, |
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plotlevel = 0 |
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| ) |
ASAP SD task: fit a spectral line
Keyword arguments:
infile -- name of input SD dataset
default: none - must input file name
example: 'mysd.asap'
See sdcal for allowed formats.
antenna -- antenna name or id (only effective for MS input).
fluxunit -- units for line flux
options: (str) 'K','Jy',''
default: '' (keep current fluxunit)
WARNING: For GBT data, see description below.
>>> fluxunit expandable parameter
telescopeparm -- the telescope characteristics
options: (str) name or (list) list of gain info
default: '' (none set)
example: if telescopeparm='', it tries to get the telescope
name from the data.
Full antenna parameters (diameter,ap.eff.) known
to ASAP are
'ATPKSMB', 'ATPKSHOH', 'ATMOPRA', 'DSS-43',
'CEDUNA','HOBART'. For GBT, it fixes default fluxunit
to 'K' first then convert to a new fluxunit.
telescopeparm=[104.9,0.43] diameter(m), ap.eff.
telescopeparm=[0.743] gain in Jy/K
telescopeparm='FIX' to change default fluxunit
see description below
specunit -- units for spectral axis
options: (str) 'channel','km/s','GHz','MHz','kHz','Hz',''
default: '' (=current)
example: this will be the units for maskline
>>> specunit expandable parameters
restfreq -- rest frequency
available type includes float, int, string, list of float,
list of int, list of string, and list of dictionary. the
default unit of restfreq in case of float, int, or string
without unit is Hz. string input can be a value only
(treated as Hz) or a value followed by unit for which 'GHz',
'MHz','kHz',and 'Hz' are available.
a list can be used to set different rest frequencies for
each IF. the length of list input must be nIF. dictionary
input should be a pair of molecule name and frequency with
keys of 'name' and 'value', respectively. values in the
dictionary input follows the same manner as for single
float or string input.
example: 345.796
'1420MHz'
[345.8, 347.0, 356.7]
['345.8MHz', '347.0MHz', '356.7MHz']
[{'name':'CO','value':345}]
frame -- frequency frame for spectral axis
options: (str) 'LSRK','REST','TOPO','LSRD','BARY',
'GEO','GALACTO','LGROUP','CMB'
default: currently set frame in scantable
WARNING: frame='REST' not yet implemented
doppler -- doppler mode
options: (str) 'RADIO','OPTICAL','Z','BETA','GAMMA'
default: currently set doppler in scantable
scanlist -- list of scan numbers to process
default: [] (use all scans)
example: [21,22,23,24]
field -- selection string for selecting scans by name
default: '' (no name selection)
example: 'FLS3a*'
this selection is in addition to scanlist and iflist
iflist -- list of IF id numbers to select
default: [] (use all IFs)
example: [15]
pollist -- list of polarization id numbers to select
default: [] (use all polarizations)
example: [1]
fitfunc -- function for fitting
options: (str) 'gauss','lorentz'
default: 'gauss'
fitmode -- mode for fitting
options: (str) 'list','auto','interact'
default: 'auto'
example: 'list' will use maskline to define regions to
fit for lines with nfit in each
'auto' will use the linefinder to fit for lines
using the following parameters
'interact' allows adding and deleting mask
regions by drawing rectangles on the plot
with mouse. Draw a rectangle with LEFT-mouse
to ADD the region to the mask and with RIGHT-mouse
to DELETE the region.
>>> fitmode expandable parameters
thresh -- S/N threshold for linefinder
default: 5
example: a single channel S/N ratio above which the channel is
considered to be a detection
min_nchan -- minimum number of consecutive channels for linefinder
default: 3
example: minimum number of consecutive channels required to pass threshold
avg_limit -- channel averaging for broad lines
default: 4
example: a number of consecutive channels not greater than
this parameter can be averaged to search for broad lines
box_size -- running mean box size
default: 0.2
example: a running mean box size specified as a fraction
of the total spectrum length
edge -- channels to drop at beginning and end of spectrum
default: 0
example: [1000] drops 1000 channels at beginning AND end
[1000,500] drops 1000 from beginning and 500 from end
Note: For bad baselines threshold should be increased,
and avg_limit decreased (or even switched off completely by
setting this parameter to 1) to avoid detecting baseline
undulations instead of real lines.
maskline -- list of mask regions to INCLUDE in LINE fitting
default: all
example: maskline=[[3900,4300]] for a single region, or
maskline=[[3900,4300],[5000,5400]] for two, etc.
invertmask -- invert mask (EXCLUDE masklist instead)
options: (bool) True, False
default: False
example: invertmask=True, then will make one region that is
the exclusion of the maskline regions
nfit -- list of number of gaussian/lorentzian lines to fit in in maskline region (ignored when fitmode='auto')
default: 0 (no fitting)
example: nfit=[1] for single line in single region,
nfit=[2] for two lines in single region,
nfit=[1,1] for single lines in each of two regions, etc.
outfile -- name of output file for fit results
default: no output fit file
example: 'mysd.fit'
overwrite -- overwrite the outfile if already exists
options: (bool) True, False
default: False
plotlevel -- control for plotting of results
options: (int) 0=none, 1=some, 2=more
default: 0 (no plotting)
example: plotlevel=1 plots fit
plotlevel=2 plots fit and residual
no hardcopy available for fitter
WARNING: be careful plotting OTF data with lots of fields
-------------------------------------------------------------------
Returns a Python dictionary of line statistics
keys: 'peak','cent','fwhm','nfit'
example: each value is a list of lists with one list of
2 entries [fitvalue,error] per component.
e.g. xstat['peak']=[[234.9, 4.8],[234.2, 5.3]]
for 2 components.
DESCRIPTION:
Task sdfit is a basic line-fitter for single-dish spectra.
It assumes that the spectra have been calibrated in sdcal
or sdreduce.
Furthermore, it assumes that any selection of scans, IFs,
polarizations, and time and channel averaging/smoothing has
also already been done (in other sd tasks) as there are no controls
for these. Note that you can use sdsave to do selection, writing
out a new scantable.
Note that multiple scans, IFs, and polarizations can in principle
be handled, but we recommend that you use scanlist, field, iflist,
and pollist to give a single selection for each fit.
Currently, you can choose Gaussian or Lorentzian profile as a
fitting model.
For complicated spectra, sdfit does not do a good job of
"auto-guessing" the starting model for the fit. We recommend
you use sd.fitter in the toolkit which has more options, such
as fixing components in the fit and supplying starting guesses
by hand.
WARNING: sdfit will currently return the fit for the first
row in the scantable.
ASAP recognizes the data of the "AT" telescopes, but currently
does not know about the GBT or any other telescope. This task
does know about GBT. Telescope name is obtained from the data.
If you wish to change the fluxunit (see below), and telescopeparm='',
for the AT telescopes it will use internal telescope parameters for
flux conversion. For GBT, it will use an approximate aperture
efficiency conversion. If you give telescopeparm a list, then
if the list has a single float it is assumed to be the gain in Jy/K,
if two or more elements they are assumed to be telescope diameter (m)
and aperture efficiency respectively.
WARNING for the GBT raw SDFITS format data as input:
SDtasks are able to handle GBT raw SDFITS format data since the
data filler is available. However, the functionality is not well
tested yet, so that there may be unknown bugs. Definition at line 13 of file sdfit.py.
References task_sdfit.sdfit(), and vla_uvfits_line_sf.verify.
1.8.0