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imagepol.fractotpol - Function

	Package	general
	Module	images
	Tool	imagepol

Fractional total polarization

Synopsis
fractotpol(debias, clip, sigma, outfile)

Arguments

debias	in	Debias the total polarized intensity ?
		Allowed:	T or F
		Default:	F
clip	in	Clip level for auto-sigma determination
		Allowed:	Float
		Default:	10
sigma	in	Standard deviation of thermal noise
		Allowed:	Float
		Default:	Auto determined
outfile	in	Output image file name
		Allowed:	String
		Default:	Unset

Returns
Image tool or fail

Description
This function (short-hand name ftp) returns the fractional linear polarization; $\sqrt{(Q^2+U^2+V^2)}$/I.

You may optionally debias the polarized intensity. This requires the standard deviation of the thermal noise. You can either supply it if you know it, or it will be worked out for you with outliers from the mean clipped at the specified level.

If your image contains only Q and U, or only V, then just those components contribute to the total polarized intensity.

Example

- p := imagepol('stokes.cube')
- ftp := p.fractotpol()