1.1.1.0 image.fitpolynomial

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image.fitpolynomial - Function

1.1.1 Fit 1-dimensional polynomials to profiles
Description

This function fits 1-dimensional polynomials to profiles and subtracts the fits. You specify the order of the polynomial via the order argument. The returned on-the-fly Image tool holds the residual image. You can optionally also write out the fitted image.

The output mask is a copy of the default input pixel mask (if any); the OTF mask does not contribute to the output mask. Any other input pixel masks will not be copied. Use function maskhandler if you need to copy other masks too. Use function calcmask if you need to apply the OTF mask to the output.

"""
#
print "\t----\t fitpolynomial Ex 1 \t----"
ia.maketestimage(’hcn’,overwrite=true)
myim = ia.fitpolynomial(order=2, axis=1) # OTF Image tool is virtual
print myim.summary()
myim.done()
ia.close()
#
"""

"""
#
print "\t----\t fitpolynomial Ex 2 \t----"
ia.fromshape(shape=[128,128,64,4]) # RA/DEC/FREQ/STOKES
# Specify pixels to fit via mask
mask = ’indexin(3, [1:20, 30, 35, 50:60, 90:128])’ # LEL’s are 1-rel!
myim = ia.fitpolynomial(order=2, mask=mask, axis=2) # axis 3 (0-rel)
print myim.summary()
myim.done()
ia.close()
#
"""

This example can be thought of as an image-based continuum substraction. You specify the axis and the pixels where the spectrum is line free (continuum), do the fit and create an on-the-fly image tool attached to the residual (continuum subtracted) image.

Arguments


Inputs
residfile	Output fitted residuals image file name. Default is unset.
	allowed:	string
	Default:
fitfile	Output fitted image file name. Default is unset.
	allowed:	string
	Default:
sigmafile	Input weights image for fitting. Default is unset.
	allowed:	string
	Default:
axis	The profile axis to fit, Default is spectral axis if it exists else last axis.
	allowed:	int
	Default:	-1
order	The order of the polynomial
	allowed:	int
	Default:	0
region	The region of interest. Default is whole image.
	allowed:	any
	Default:	record
mask	OTF mask, Boolean LEL expression or mask region. Default is none.
	allowed:	any
	Default:	variant
overwrite	Overwrite (unprompted) pre-existing output files?
	allowed:	bool
	Default:	false

Returns
casaimage

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