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0.1.102 sdbaseline2old
Requires:
Synopsis
ASAP SD task [DEPRECATED]: Fit/subtract a spectral baseline
Description
### DEPRECATION WARNING
#################################################
This task will be removed in CASA 5.1. To a very great extent, the
functionality of this task with MeasurementSet format is replicated with
sdbaseline.
#########################################################################
Task sdbaseline2old performs baseline fitting/removal for single-dish spectra.
Arguments
Inputs |
| ||
infile |
| name of input SD dataset
| |
| allowed: | string |
|
| Default: |
|
|
antenna |
| select an antenna name or ID, e.g. ’PM03’ (only effective
for MS input)
| |
| allowed: | any |
|
| Default: | variant 0 |
|
row |
| select data by row IDs, e.g. ’3,5,7’ (”=all)
| |
| allowed: | string |
|
| Default: |
|
|
field |
| select data by field IDs and names, e.g. ’3C2*’ (”=all)
| |
| allowed: | string |
|
| Default: |
|
|
spw |
| select data by IF IDs (spectral windows), e.g. ’3,5,7’
(”=all)
| |
| allowed: | string |
|
| Default: |
|
|
restfreq |
| the rest frequency, e.g. ’1.41GHz’ (default unit: Hz) (see
examples in help)
| |
| allowed: | any |
|
| Default: | variant
|
|
frame |
| frequency reference frame (”=current)
| |
| allowed: | string |
|
| Default: |
|
|
doppler |
| doppler convention (”=current). Effective only when
spw selection is in velocity unit.
| |
| allowed: | string |
|
| Default: |
|
|
timerange |
| select data by time range, e.g. ’09:14:0~09:54:0’ (”=all)
(see examples in help)
| |
| allowed: | string |
|
| Default: |
|
|
scan |
| select data by scan numbers, e.g. ’21~23’ (”=all)
| |
| allowed: | string |
|
| Default: |
|
|
pol |
| select data by polarization IDs, e.g. ’0,1’ (”=all)
| |
| allowed: | string |
|
| Default: |
|
|
blmode |
| baselining mode (’subtract’ or ’apply’)
| |
| allowed: | string |
|
| Default: | subtract |
|
blparam |
| per spectrum fit parameters
| |
| allowed: | any |
|
| Default: | variant
|
|
bltable |
| name of baseline table
| |
| allowed: | string |
|
| Default: |
|
|
outfile |
| name of output file (See a WARNING in help)
| |
| allowed: | string |
|
| Default: |
|
|
overwrite |
| overwrite the output file if already exists
| |
| allowed: | bool |
|
| Default: | False |
|
keeprows |
| keep all rows of input scantable in output table [True,
False]
| |
| allowed: | bool |
|
| Default: | False |
|
void
Example
-----------------
Keyword arguments
-----------------
infile -- name of input SD dataset
antenna -- select an antenna name or ID
default: 0
example: ’PM03’
NOTE this parameter is effective only for MS input
field -- select data by field IDs and names
default: ’’ (use all fields)
example: field=’3C2*’ (all names starting with 3C2)
field=’0,4,5~7’ (field IDs 0,4,5,6,7)
field=’0,3C273’ (field ID 0 or field named 3C273)
this selection is in addition to the other selections to data
spw -- select data by IF IDs (spectral windows)/channels
default: ’’ (use all IFs and channels)
example: spw=’3,5,7’ (IF IDs 3,5,7; all channels)
spw=’<2’ (IF IDs less than 2, i.e., 0,1; all channels)
spw=’30~45GHz’ (IF IDs with the center frequencies in range 30-45GHz; all channels)
spw=’0:5~61’ (IF ID 0; channels 5 to 61; all channels)
spw=’3:10~20;50~60’ (select multiple channel ranges within IF ID 3)
spw=’3:10~20,4:0~30’ (select different channel ranges for IF IDs 3 and 4)
spw=’1~4;6:15~48’ (for channels 15 through 48 for IF IDs 1,2,3,4 and 6)
this selection is in addition to the other selections to data
>>> spw expandable parameter
restfreq -- the 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 number of IFs.
dictionary input should be a pair of line name and
frequency with keys of ’name’ and ’value’, respectively.
values in the dictionary input follows the same manner as
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 reference frame
options: ’LSRK’, ’TOPO’, ’LSRD’, ’BARY’, ’GALACTO’, ’LGROUP’, ’CMB’
default: ’’ (keep current frame in data)
doppler -- doppler convention (effective only when spw is in
velocity unit)
options: ’RADIO’, ’OPTICAL’, ’Z’, ’BETA’, or ’GAMMA’
default: ’’ (keep current doppler setting in data)
timerange -- select data by time range
default: ’’ (use all)
example: timerange = ’YYYY/MM/DD/hh:mm:ss~YYYY/MM/DD/hh:mm:ss’
Note: YYYY/MM/DD can be dropped as needed:
timerange=’09:14:00~09:54:00’ # this time range
timerange=’09:44:00’ # data within one integration of time
timerange=’>10:24:00’ # data after this time
timerange=’09:44:00+00:13:00’ #data 13 minutes after time
this selection is in addition to the other selections to data
scan -- select data by scan numbers
default: ’’ (use all scans)
example: scan=’21~23’ (scan IDs 21,22,23)
this selection is in addition to the other selections to data
pol -- select data by polarization IDs
default: ’’ (use all polarizations)
example: pol=’0,1’ (polarization IDs 0,1)
this selection is in addition to the other selections to data
blmode -- ’subtract’ or ’apply’
default: ’subtract’
>>> blmode expandable parameter
blparam -- per spectrum fit parameters. it must be a list of
dictionary. Each dictionary corresponds to each
spectrum and must contain the following keys and values:
’row’: row number,
’blfunc’: function name. available ones include
’poly’, ’chebyshev’, ’cspline’ and ’sinusoid’,
’order’: maximum order of polynomial. needed when
blfunc=’poly’ or ’chebyshev’,
’npiece’: number or piecewise polynomial.
needed when blfunc=’cspline’ and
’nwave’: a list of sinusoidal wave numbers.
needed when blfunc=’sinusoid’.
example: [{’row’:0,’blfunc’:’poly’,’order’:5},
{’row’:1,’blfunc’:’chebyshev’,’order’:10},
{’row’:2,’blfunc’:’cspline’,’npiece’:4},
{’row’:3,’blfunc’:’sinusoid’,’nwave’:[0,1,2,3]}, ...]
bltable -- the name of baseline table (bltable=’’ would subtract baseline without
creating bltable. mandatory when blmode=’apply’)
default: ’’
outfile -- name of output file
default: ’’ (<infile>_bs)
overwrite -- overwrite existing outfile and bltable or not
options: (bool) True, False
default: False
-----------
DESCRIPTION
-----------
Task sdbaseline2old performs baseline fitting/removal for single-dish spectra.
-----------------------
BASELINE MODEL FUNCTION
-----------------------
The list of available model functions are shown above (see Keyword arguments
section). In general ’cspline’ or ’chebyshev’ are recommended since they are
more stable than others. ’poly’ will work for lower order but will be unstable
for higher order fitting. ’sinusoid’ is kind of special mode that will be
useful for the data that clearly shows standing wave in the spectral baseline.
----------------------------------
SIGMA CLIPPING (ITERATIVE FITTING)
----------------------------------
In general least square fitting is strongly affected by an extreme data
so that the resulting fit makes worse. Sigma clipping is an iterative
baseline fitting with data clipping based on a certain threshold. Threshold
is set as a certain factor times rms of the resulting (baseline subtracted)
spectra. If sigma clipping is on, baseline fit/removal is performed several
times. After each baseline subtraction, the data whose absolute value is
above threshold are detected and those data are excluded from the next round
of fitting. By using sigma clipping, extreme data are excluded from the
fit so that resulting fit is more robust.
The user is able to control a multiplication factor using parameter
clipthresh for clipping threshold based on rms. Actual threshold for sigma
clipping will be (clipthresh) x (rms of spectra). Also, the user can specify
number of maximum iteration to the parameter clipniter.
In general, sigma clipping will lower the performance since it increases
number of fits per spectra. However, it is strongly recommended to turn
on sigma clipping unless you are sure that the data is free from any kind
of extreme values that may affect the fit.
More information about CASA may be found at the
CASA web page
Copyright © 2016 Associated Universities Inc., Washington, D.C.
This code is available under the terms of the GNU General Public Lincense
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