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autoflag.setsprej - Function

	Package	synthesis
	Module	autoflag
	Tool	autoflag

Sets up the spectral rejection flagging method

Synopsis
setsprej(ndeg, rowthr, rowhw, norow, spwid, fq, chan, region, column, expr, fignore)

Description

The sprej method works by fitting a user-specified segment of the spectrum (presumably, the continuum) by a polynomial. It then flags entire rows based on the chi-square statistic of the fit, in a manner similar to timemed. Please refer to setimemed for detailed math, substituting $\chi^{2}_{bt}$ for M_bt. The value that is actually fitted is specified via the expr parameter (see the general autoflag module description for details).

The segement to be fitted can be specified as a range of channel indices (1-based) or frequencies. Frequencies may be given as string measures ("1.4GHz") or float values (units of MHz assumed). A vector of two values [C1,C2] specifies the segment from C1 to C2, inclusive. Several disjoint segments may be specified with a 2N vector or a (2,N) matrix.

For a measurement set containing multiple spectral windows, you can set the region argument to a record of records, with each sub-record containing spwid and fq and/or chan fields, specifying the segments of a specific spectral window. See examples below.

Arguments

ndeg		Number of degrees for polynomial
		Allowed:	Int
		Default:	2
rowthr		Flagging threshold, in MADs of $\chi^{2}_{}$
		Allowed:	numeric (real)
		Default:	5
rowhw		Half-window for the sliding median
		Allowed:	Int
		Default:	6
norow		Disable row flagging
		Allowed:	Boolean
		Default:	F
spwid		Spectral window number (1-based), or [] or F for all windows
		Allowed:	F or [] or Int
		Default:	F
fq		Range of frequencies
		Allowed:	2N or (2,N) array of Strings w/units or Floats
		Default:	F
chan		Range of channels (1-based). Either ``fq'' or ``chan'' must be specified.
		Allowed:	2N or (2,N) array of Ints
		Default:	F
region		A compound spectral segment specification (see example)
		Allowed:	Record of records
		Default:	F
column		Which column to base flagging on
		Allowed:	"DATA", "MODEL" or "CORR"
		Default:	"DATA"
expr		Expression to use
		Allowed:	see text
		Default:	"ABS I"
fignore		Ignore existing flags
		Allowed:	Bool
		Default:	F

Example

- af:=autoflag('3C273XC1.MS')
- af.setdata()
# use segments 807-807.5 and 809-809.5 MHz for fitting
- af.setsprej(fq=[807,807.5,809,809.5)) 
...
# use channels 10-20 and 30-40
- af.setsprej(chan=[[10,20],[30,40]])
...
# use different segements in different spectral windows
- region := [=]
- region[1] := [ spwid=1,fq="1.4GHz 1.401GHz" ]
- region[2] := [ spwid=2,chan=[10,20] ]
- region[3] := [ spwid=4,chan=[50,60] ]
- af.setsprej(region=region)