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image.fitpolynomial - Function

	Package	general
	Module	images
	Tool	image

Fit 1-dimensional polynomials to profiles

Synopsis
fitpolynomial(residfile, fitfile, sigmafile, axis, order, region, mask, overwrite)

Arguments

residfile	in	Output fitted residuals image file name
		Allowed:	String or unset
		Default:	unset
fitfile	in	Output fitted image file name
		Allowed:	String or unset
		Default:	unset
sigmafile	in	Input weights image for fitting
		Allowed:	String or unset
		Default:	unset
axis	in	The profile axis to fit
		Allowed:	Integer or unset
		Default:	Spectral axis if exists else last
order	in	The order of the polynomial
		Allowed:	Integer or unset
		Default:	0
region	in	The region of interest
		Allowed:	Region tool
		Default:	Whole image
mask	in	OTF mask
		Allowed:	Boolean LEL expression or mask region
		Default:	None
overwrite	in	Overwrite (unprompted) pre-existing output files ?
		Allowed:	T or F
		Default:	F

Returns
Image tool or fail

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 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.

Example

- myim := image('hcn')
- myim2 := myim.fitpolynomial(order=2, axis=3)      # Image tool is virtual

Example

- myim := image('hcn')
- mask := 'indexin(3, [1:20, 30, 35, 50:60, 90:128])'        # Specify pixels to fit via mask on 
- myim2 := myim.fitpolynomial(order=2, mask=mask, axis=3)    # axis 3

This example could be thought of, for example, as an image-based continuum substraction. You specify the axis and the pixels where the spectrum is line free (continuum), do the fit and write out the residual (continuum subtracted) image.