casacore::LatticeFit Class Reference

Fit every line of pixels parallel to any axis in a Lattice. More...

#include <LatticeFit.h>

Static Public Member Functions
static uInt	fitProfiles (Lattice< Float > &outImage, Vector< Float > &fittedParameters, LinearFit< Float > &fitter, const Lattice< Float > &inImage, uInt whichAxis, const Vector< Bool > &fitMask, Bool returnResiduals)
	Fit baseline to lattice.
static uInt	fitProfiles (MaskedLattice< Float > pOutFit, MaskedLattice< Float > pOutResid, MaskedLattice< Float > &in, Lattice< Float > *pSigma, LinearFit< Float > &fitter, uInt axis, Bool showProgress=False)
	Fit baseline to MaskedLattice.

Detailed Description

Fit every line of pixels parallel to any axis in a Lattice.

Prerequisite

Synopsis

For every line in the lattice parallel to axis number whichAxis (often axis number 2, typically the frequency axis in a spectral line cube) independently fit the functions in fitter at the positions where fitMask is true.

Example

Suppose one wanted to subtract a linear polynomial from every spectrum (3d axis) in an image. One could do this as follows:

 Image<Float> myImage("myimage"); // Get the image
 uInt nchan = myImage.shape()(2); // 0 relative axis number
 // Set up the fitter
 Polynomial<AutoDiff<Float> > linear(1);    
 LinearFitSVD<Float> fitter;
 fitter.setFunction(linear);
 Vector<Float> fittedParameters,
 
 // Set up a mask indicating what channels we want to fit over. We want
 // to fit over all channels.
 Vector<Bool> fitMask(nchan); fitMask = True;
 
 // Do the fit. True means subtract the fit from the model. In this case,
 // We overwrite the input with the output.
 fitProfiles (myImage, fittedParameters,fitter, myImage, 2, fitMask, True);

Motivation

Baseline fitting/continuum subtraction are important functions. This function essentially implements the IMLIN algorithm.

To Do

Save the model parameters in an (optional) other lattice.
Use logging classes, rather than the raw GlishSysEventSource.
Allow per-pixel weights.
Allow non-linear as well as linear LSQ fits.

Definition at line 96 of file LatticeFit.h.

Member Function Documentation

static uInt casacore::LatticeFit::fitProfiles	(	MaskedLattice< Float > *	pOutFit,
		MaskedLattice< Float > *	pOutResid,
		MaskedLattice< Float > &	in,
		Lattice< Float > *	pSigma,
		LinearFit< Float > &	fitter,
		uInt	axis,
		Bool	showProgress = `False`
	)			`[static]`

Fit baseline to MaskedLattice.

Fit and residuals can be optionally written (leave pointers at zero to not write out these lattices) You can optionally specify a weights lattice (1.0 if not given).

static uInt casacore::LatticeFit::fitProfiles	(	Lattice< Float > &	outImage,
		Vector< Float > &	fittedParameters,
		LinearFit< Float > &	fitter,
		const Lattice< Float > &	inImage,
		uInt	whichAxis,
		const Vector< Bool > &	fitMask,
		Bool	returnResiduals
	)			`[static]`

Fit baseline to lattice.

Presently the fit parameters, other than the last one(s) in fitter, are lost. If returnResiduals is True, return data-fit, otherwise return the fit. For baseline and continuum subtraction, returnResiduals would normally be True.

The documentation for this class was generated from the following file:

casacore/lattices/LatticeMath/LatticeFit.h