casa::ConstantSpectrum Class Reference

Model the spectral variation with a constant. More...

#include <ConstantSpectrum.h>

Inheritance diagram for casa::ConstantSpectrum:

List of all members.

Public Member Functions
	ConstantSpectrum ()
	The default constructor is the only one you really need as this class has no parameters!
	ConstantSpectrum (const ConstantSpectrum &other)
	The copy constructor uses copy semantics.
virtual	~ConstantSpectrum ()
	The destructor does nothing.
ConstantSpectrum &	operator= (const ConstantSpectrum &other)
	The assignment operator uses copy semantics.
virtual ComponentType::SpectralShape	type () const
	return the actual spectral type.
virtual Double	sample (const MFrequency &centerFrequency) const
	Return the scaling factor that indicates the flux is at the specified frequency assuming the flux at the reference frequency is one.
virtual void	sample (Vector< Double > &scale, const Vector< MFrequency::MVType > &frequencies, const MFrequency::Ref &refFrame) const
	Same as the previous function except that many frequencies can be sampled at once.
virtual SpectralModel *	clone () const
	Return a pointer to a copy of this object upcast to a SpectralModel object.
virtual uInt	nParameters () const
	return the number of parameters.
virtual void	setParameters (const Vector< Double > &newSpectralParms)
virtual Vector< Double >	parameters () const
virtual void	setErrors (const Vector< Double > &newSpectralErrs)
virtual Vector< Double >	errors () const
virtual Bool	fromRecord (String &errorMessage, const RecordInterface &record)
	These functions convert between a Record and a ConstantSpectrum.
virtual Bool	toRecord (String &errorMessage, RecordInterface &record) const
	Convert the class to an Record representation.
virtual Bool	convertUnit (String &errorMessage, const RecordInterface &record)
	Convert the parameters of the spectrum to the specified units.
virtual Bool	ok () const
	Function which checks the internal data of this class for consistant values.

---

Detailed Description

Model the spectral variation with a constant.

Intended use:

Public interface

 <h3>Review Status</h3><dl><dt>Date Reviewed:<dd>yyyy/mm/dd<dt>Test programs:<dd>tConstantSpectrum<dt>Demo programs:<dd>dConstantSpectrum</dl> 

Prerequisite

• SpectralModel

Synopsis

This class models the spectral variation of a component as constant, ie. unchanging with frequency. It is the simplest possible model for spectral variation.

This class like the other spectral models becomes more useful when used through the SkyComponent class, which incorperates the flux and spatial variation of the emission, or through the ComponentList class, which handles groups of SkyComponent objects.

Because the flux is constant with frequency the concept of a reference frequency is meaningless with this class. But it can still be accessed using the refFrequency and setRefFrequency. However changing its value will not affect the behaviour of this class.

This class does not have any parameters and the nParameters function will return zero. It is an error that will generate an exception (in Debug mode) to call the setParameters and parameters functions with anything other than a zero length vector.

The sample functions always return 1.0.

This class also contains functions (toRecord & fromRecord) which perform the conversion between Records and ConstantSpectrum objects. These functions define how a ConstantSpectrum object is represented in glish. The format of the record that is generated and accepted by these functions is:

    c := [type = 'constant',
          frequency = [type = 'frequency',
                       refer = 'lsr',
                       m0 = [value = 1, unit = 'GHz']
                      ]
         ]

The frequency field contains a record representation of a frequency measure and its format is defined in the Measures module. Its refer field defines the reference frame for the direction and the m0 field defines the value of the reference frequency. The parsing of the type field is case insensitive.

Example

Its hard to think of a good example for this class as it is basically does nothing! In this example the spectral variation of a component is set to to a constant value.

    SkyComponent myComp(...);
    ..\.
    if (myComp.spectrum().type() != ComponentType::CONSTANT_SPECTRUM) {
      myComp.spectrum() = ConstantSpectrum();
    }

Motivation

A ConstantSpectrum class is needed for users who are not interested in modelling any spectral variation in their components.

To Do

• Nothing I hope!

Definition at line 124 of file ConstantSpectrum.h.

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Constructor & Destructor Documentation

casa::ConstantSpectrum::ConstantSpectrum

(

)

The default constructor is the only one you really need as this class has no parameters!

casa::ConstantSpectrum::ConstantSpectrum

(

const ConstantSpectrum &

other

)

The copy constructor uses copy semantics.

virtual casa::ConstantSpectrum::~ConstantSpectrum

(

)

[virtual]

The destructor does nothing.

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Member Function Documentation

virtual SpectralModel* casa::ConstantSpectrum::clone

(

)

const [virtual]

Return a pointer to a copy of this object upcast to a SpectralModel object.

The class that uses this function is responsible for deleting the pointer. This is used to implement a virtual copy constructor.

Implements casa::SpectralModel.

virtual Bool casa::ConstantSpectrum::convertUnit	(	String &	errorMessage,
		const RecordInterface &	record
	)		[virtual]

Convert the parameters of the spectrum to the specified units.

As a constant spectrum has no parameters this function does nothing and always returns True.

Implements casa::SpectralModel.

virtual Vector<Double> casa::ConstantSpectrum::errors

(

)

const [virtual]

Implements casa::SpectralModel.

virtual Bool casa::ConstantSpectrum::fromRecord	(	String &	errorMessage,
		const RecordInterface &	record
	)		[virtual]

These functions convert between a Record and a ConstantSpectrum.

These functions define how a ConstantSpectrum object is represented in glish and this is detailed in the synopsis above. These functions return False if the record is malformed and append an error message to the supplied string giving the reason.

Implements casa::SpectralModel.

virtual uInt casa::ConstantSpectrum::nParameters

(

)

const [virtual]

return the number of parameters.

There are no parameters for this spectral model. So calling setParameters or parameters with anything other than a zero length Vector will throw an exception (when compiled in debug mode).

Implements casa::SpectralModel.

virtual Bool casa::ConstantSpectrum::ok

(

)

const [virtual]

Function which checks the internal data of this class for consistant values.

Returns True if everything is fine otherwise returns False.

Reimplemented from casa::SpectralModel.

ConstantSpectrum& casa::ConstantSpectrum::operator=

(

const ConstantSpectrum &

other

)

The assignment operator uses copy semantics.

virtual Vector<Double> casa::ConstantSpectrum::parameters

(

)

const [virtual]

Implements casa::SpectralModel.

virtual Double casa::ConstantSpectrum::sample

(

const MFrequency &

centerFrequency

)

const [virtual]

Return the scaling factor that indicates the flux is at the specified frequency assuming the flux at the reference frequency is one.

This function always returns one, as the spectrum is constant.

Implements casa::SpectralModel.

virtual void casa::ConstantSpectrum::sample	(	Vector< Double > &	scale,
		const Vector< MFrequency::MVType > &	frequencies,
		const MFrequency::Ref &	refFrame
	)		const [virtual]

Same as the previous function except that many frequencies can be sampled at once.

The reference frame must be the same for all the specified frequencies. Uses a customised implementation.

Implements casa::SpectralModel.

virtual void casa::ConstantSpectrum::setErrors

(

const Vector< Double > &

newSpectralErrs

)

[virtual]

Implements casa::SpectralModel.

virtual void casa::ConstantSpectrum::setParameters

(

const Vector< Double > &

newSpectralParms

)

[virtual]

Implements casa::SpectralModel.

virtual Bool casa::ConstantSpectrum::toRecord	(	String &	error,
		RecordInterface &	outRecord
	)		const [virtual]

Convert the class to an Record representation.

The input record may already contain fields and these fields may be silently overridden. New fields may be added to the input Record. If the transformation succeeds then the error String is unchanged and the function returns True. Otherwise the function returns False and appends an error message to the supplied String giving the reason why the conversion failed.

Implements casa::SpectralModel.

virtual ComponentType::SpectralShape casa::ConstantSpectrum::type

(

)

const [virtual]

return the actual spectral type.

This function always returns ComponentType::CONSTANT_SPECTRUM

Implements casa::SpectralModel.

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

• casacore/components/ComponentModels/ConstantSpectrum.h