1.1.1.0 image.continuumsub

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image.continuumsub - Function

1.1.1 Image plane continuum subtraction

Description

This function packages the relevant image tool functionality for simple specification and application of image plane continuum subtraction. All that is required of the input image is that it have a non-degenerate spectral axis.

The user specifies region, the region of the input image over which continuum subtraction is desired (otherwise the whole image will be treated); channels, the subset of channels on the spectral axis to use in the continuum estimation, specified as a vector; fitorder, the polynomial order to use in the estimation. Optionally, output line and continuum images may be written by specifying outline and outcont, respectively. If outline is not specified, a virtual image tool is all that is produced. If outcont is not specified, the output continuum image will be written in ’continuumsub.im’. Note that the pol parameter is no longer supported; one should use the region parameter if polarization selection is desired, in conformance with other ia tool methods.

Arguments


Inputs
outline	Output line image filename. Default is unset.
	allowed:	string
	Default:
outcont	Output continuum image filename
	allowed:	string
	Default:	continuumsub.im
region	Region selection. See ”help par.region” for details. Default is to use the full image.
	allowed:	any
	Default:	variant
channels	Channels to use for continuum estimation. Default is all.
	allowed:	intArray
	Default:	-1
pol	THIS PARAMETER IS NO LONGER SUPPORTED. USE THE region PARAMETER TO CHOOSE WHICH POLARIZATIONS YOU WOULD LIKE TO PROCESS
	allowed:	string
	Default:
fitorder	Polynomial order for continuum estimation
	allowed:	int
	Default:	0
overwrite	Auto-overwrite output files if they exist?
	allowed:	bool
	Default:	false

Returns
image

Example

Fit a second order polynomial (fitorder=2) to channels 3-8 and 54-60 (python’s
range function includes the lower limit and excludes the upper limit)
to an RA x Dec x Frequency x Stokes cube.

ia.open("myimage.im")

# select stokes plane 1 on which to perform the fit, as well
# as a box of pixels with blc=25,25 and trc=75,75 in the direction
# plane, and channels 0 to 100. This will be the portion of the cube
# from which the fit is subtracted
reg = rb.box(blc=[25, 25, 0, 1], trc=[75, 75, 100, 1])
csub = ia.continuumsub(region=reg, channels=range(3,9)+range(54,61), fitorder=2)

# do stuff with original image (ia) and csub image tools as necessary and
# finally close them
ia.done()
csub.done()

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