Definition of a Measure column in a Table. More...

#include <TableMeasDesc.h>

Inheritance diagram for casacore::TableMeasDesc< M >:

Public Member Functions
	TableMeasDesc (const TableMeasValueDesc &)
	Constructor with measure value descriptor. More...

	TableMeasDesc (const TableMeasValueDesc &, const Vector< Unit > &)
	Constructor with measure value descriptor and Vector of Units. More...

	TableMeasDesc (const TableMeasValueDesc &, const TableMeasRefDesc &)
	Constructor with value and reference descriptors. More...

	TableMeasDesc (const TableMeasValueDesc &, const TableMeasRefDesc &, const Vector< Unit > &)
	Constructor with value and reference descriptors and Vector of Units. More...

virtual TableMeasDescBase *	clone () const
	Clone the object. More...

	TableMeasDesc (const TableMeasDesc< M > &that)
	Copy constructor (copy semantics). More...

	~TableMeasDesc ()

TableMeasDesc< M > &	operator= (const TableMeasDesc< M > &that)
	Assignment operator (copy semantics) More...

Public Member Functions inherited from casacore::TableMeasDescBase
	TableMeasDescBase ()
	Null constructor. More...

	TableMeasDescBase (const TableMeasValueDesc &, const TableMeasRefDesc &)
	Constructor with value and reference descriptors. More...

	TableMeasDescBase (const TableMeasDescBase &that)
	Copy constructor. More...

virtual	~TableMeasDescBase ()

TableMeasDescBase &	operator= (const TableMeasDescBase &that)
	Assignment operator. More...

void	write (TableDesc &)
	Makes the descriptor persistent. More...

void	write (Table &)

void	writeIfOld (const Table &)
	Make the descriptor persistent if there was no refcode vector. More...

const String &	columnName () const
	Get the name of the underlying column. More...

uInt	getRefCode () const
	Return the reference code. More...

Bool	isRefCodeVariable () const
	Returns True if the reference varies per row. More...

const String &	refColumnName () const
	Returns the name of the ref code column when the ref code is variable. More...

const TableMeasRefDesc &	getRefDesc () const
	Returns a reference to its measure reference descriptor. More...

const String &	offsetColumnName () const
	Get the name of the offset column. More...

Bool	hasOffset () const
	Returns True if an offset has been defined. More...

Bool	isOffsetVariable () const
	Returns True if the offset is variable. More...

Bool	isOffsetArray () const
	Returns True if the offset is variable and is stored in an ArrayMeasColumn, i.e., offsets are stored per element. More...

const Measure &	getOffset () const
	Returns a reference to the offset. More...

const String &	type () const
	Returns the descriptors measure type as a String. More...

uInt	refCode (const String &refString) const
	Returns the reference code for this object given a string. More...

const String &	refType (uInt refCode) const
	Translates the refCode for the descriptors measure type. More...

const Vector< Unit > &	getUnits () const
	Return the Units of the Measure values. More...

void	resetRefCode (uInt refCode)
	Reset the refCode, offset, or units. More...

void	resetOffset (const Measure &offset)

void	resetUnits (const Vector< Unit > &units)

Additional Inherited Members
Static Public Member Functions inherited from casacore::TableMeasDescBase
static TableMeasDescBase *	reconstruct (const Table &tab, const String &columnName)
	Reconstructs the object for the given table and column name. More...

static Bool	hasMeasures (const TableColumn &column)
	Does this column contain table measures? More...

Protected Member Functions inherited from casacore::TableMeasDescBase
void	initTabRef (const MeasureHolder &measHolder)
	Set the initial reference codes and types in the table. More...

void	setMeasUnits (const Measure &meas, const Vector< Quantum< Double > > &val, const Vector< Unit > &units)
	Set the measure and possible units. More...

Detailed Description

template<class M>
class casacore::TableMeasDesc< M >

Definition of a Measure column in a Table.

Intended use:

Public interface

Review Status

Reviewed By:: Bob Garwood
Date Reviewed:: 1999/12/23
Test programs:: tTableMeasures

Prerequisite

Synopsis

The TableMeasures system was created to add support for Measure columns to the Casacore Table system. Measures are not a fundamental type of the Tables system and hence cannot be represented directly. Instead a Measure column can be created with the aid of the TableMeasDesc class hierarchy. The TableMeasDesc class hierarchy creates a Measure column by associating some number of fundamental data type Table columns into a unit. The associations between these columns is represented in the column keywords of each of the columns which make up a specific Measure column.

Creating and using Measure columns is a three step process:

For each Measure column some number of columns are defined and added to the Table descriptor.
A TableMeasDesc object is used to define a (empty) Measure column from the columns created in the first step.
(RO)ScalarMeasColumns or (RO)ArrayMeasColumns objects are used to access the Measure column for the reading and writing of Measures.

Defining a Measure column (that is, steps 1 and 2 above) is the more complex operation. However, for each Measure column it is a once only operation. After a Measure column has been created its subsequent use is not much different to using "ordinary" Table columns. For information on how to use a Measure column see the (RO)ScalarMeasColumns and (RO)ArrayMeasColumns classes.

The TableMeasDesc class hierarchy contains classes for defining each component of the Measures to be contained in column. A TableMeasOffsetDesc is used to specify the offset component, a TableMeasRefDesc to set up the reference code component and a TableMeasValueDesc names the column used as the main Measure column through which the Measure column is subsequently accessed.
The final step needed to create a Measure column is the creation of a TableMeasDesc object whose constructor takes a TableMeasValueDesc and (optionally) a TableMeasRefDesc. After construction the TableMeasDesc object's write() member is used to make the the Measure column persistent within the Table.

The following examples demonstrate the creation of Measure columns using the above components. Further details about each of these components is available with each class description.
All examples write the measure description into a TableDesc object, i.e. the argument used in the TableMeasDesc::write function is a TableDesc object. It is, however, also possible to write them into a Table object which is useful if measure columns are added to an already existing table (see example 2).

Example

The following creates a MEpoch column with a fixed reference.

// Need a table to work with.

TableDesc td("measureTable_desc", "1", TableDesc::New);

td.comment() = "A test of TableMeasures class.";

// Define a column and add it to the table

// The main measure column is always an Array column of type Double

ArrayColumnDesc<Double> cdTime("Time", "An MEpoch column");

td.addColumn(cdtime);

// Create the Measure column for an MEpoch. The MEpoch in

// the column has reference code MEpoch::TAI

TableMeasRefDesc measRef(MEpoch::TAI);

TableMeasValueDesc measVal(td, "Time");

TableMeasDesc<MEpoch> mepochCol(measVal, measRef);

// write makes the Measure column persistent.

mepochCol.write(td);

// create the table with 5 rows

SetupNewTable newtab("MeasuresTable", td, Table::New);

Table tab(newtab, 5);
Same as example above, but for an already existing table.

// Need a table to work with.

TableDesc td("measureTable_desc", "1", TableDesc::New);

td.comment() = "A test of TableMeasures class.";

// Define a column and add it to the table

// The main measure column is always an Array column of type Double

ArrayColumnDesc<Double> cdTime("Time", "An MEpoch column");

td.addColumn(cdtime);

// create the table with 5 rows

SetupNewTable newtab("MeasuresTable", td, Table::New);

Table tab(newtab, 5);

// Create the Measure column for an MEpoch. The MEpoch in

// the column has reference code MEpoch::TAI

TableMeasRefDesc measRef(MEpoch::TAI);

TableMeasValueDesc measVal(tab.tableDesc(), "Time");

TableMeasDesc<MEpoch> mepochCol(measVal, measRef);

// write makes the Measure column persistent.

mepochCol.write(tab);
An MEpoch column with a variable reference code with a fixed offset:

// The following three columns will be used to set up a Scalar MEpoch

// column with variable references and offsets. 3 columns are needed.

// The "main" column where the MEpoch will be stored

ArrayColumnDesc<Double> cdTime("Time", "An MEpoch column");

// Variable (i.e., per row) reference code storage needs a column.

// The column type is either Int or String (Int is faster but String

// may be useful when browsing the table). Either a Scalar column or

// Array column can be used here dependent on whether a Scalar or

// Array Measure column is used and whether in case of an Array Measure

// column the reference code has to be variable per array element.

ScalarColumnDesc<Int> cdRef("TimeRef", "Reference column for Time");

// add the columns to the Table decriptor

td.addColumn(cdTime);

td.addColumn(cdRef);

// now create the MEpoch column.

// want a fixed offset. Offsets are Measures

MEpoch offset(MVEpoch(MVTime(1996, 5, 17), MEpoch::UTC);

TableMeasOffsetDesc offsetDesc(offset);

// the reference

TableMeasRefDesc measRef(td, "TimeRef", offsetDesc);

// the value descriptor, create and write the column

TableMeasValueDesc measVal(td, "Time");

TableMeasDesc<MEpoch> mepochCol(measVal, measRef);

mepochCol.write();

// create the table, etc

..\.
An MEpoch column with a variable reference code and offset
// Variable (per row storage of) offsets needs its own column. Measure

// offsets are Measures therefore a Measure column is needed.

ArrayColumnDesc<Double> cdOffset("OffsetCol", "Variable Offset col");

// A column for the variable reference code

ScalarColumnDesc<String> cdRef("RefCol", "Variable reference column");

// The main (value) column for the Measure column

ArrayColumnDesc<Double> cdTime("Time", "MEpoch column");

// add the column descriptors to the table

td.addColumn(cdOffset);

td.addColumn(cdRef);

td.addColumn(cdTime);

// Create the Measure column

// The offset column is itself a Measure column, but write() is not

// called

TableMeasValueDesc offsetVal(td, "OffsetCol");

TableMeasDesc<MEpoch> offset(offsetVal);

TableMeasOffsetDesc offsetDesc(offset);

// the reference

TableMeasRefDesc ref(td, "RefCol", offsetDesc);

// create the Measure column

TableMeasValueDesc val(td, "Time");

TableMeasDesc<MEpoch> mepochCol(val, ref);

mepochCol.write();

// create the table, etc

..\.

Motivation

Creating the required keyword for the definition of a Measure in a Table is somewhat complicated. This class assists in that process.

Thrown Exceptions

AipsError if a reference code string is invalid.

Definition at line 259 of file TableMeasDesc.h.

Constructor & Destructor Documentation

template<class M>

casacore::TableMeasDesc< M >::TableMeasDesc ( const TableMeasValueDesc & )

Constructor with measure value descriptor.

The Measure reference for the column will be the default reference code for M. Units for the column will be the default for the Measure type.

template<class M>

casacore::TableMeasDesc< M >::TableMeasDesc	(	const TableMeasValueDesc &	,
		const Vector< Unit > &
	)

Constructor with measure value descriptor and Vector of Units.

The Measure reference for the column will be the default reference code for the Measure type. Number of Units must be compatible with the Measure.

template<class M>

casacore::TableMeasDesc< M >::TableMeasDesc	(	const TableMeasValueDesc &	,
		const TableMeasRefDesc &
	)

Constructor with value and reference descriptors.

Units for the column will be the default for Measure type.

template<class M>

casacore::TableMeasDesc< M >::TableMeasDesc	(	const TableMeasValueDesc &	,
		const TableMeasRefDesc &	,
		const Vector< Unit > &
	)

Constructor with value and reference descriptors and Vector of Units.

Number of Units must be compatible with the Measure.

template<class M>

casacore::TableMeasDesc< M >::TableMeasDesc ( const TableMeasDesc< M > & that )

Copy constructor (copy semantics).

template<class M>

casacore::TableMeasDesc< M >::~TableMeasDesc ( )

Member Function Documentation

template<class M>

virtual TableMeasDescBase* casacore::TableMeasDesc< M >::clone ( ) const

virtual

Clone the object.

Reimplemented from casacore::TableMeasDescBase.

template<class M>

TableMeasDesc<M>& casacore::TableMeasDesc< M >::operator= ( const TableMeasDesc< M > & that )

Assignment operator (copy semantics)

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

measures/TableMeasures/TableMeasDesc.h

Public Member Functions

Additional Inherited Members

Detailed Description

template<class M> class casacore::TableMeasDesc< M >

Intended use:

Review Status

Prerequisite

Synopsis

Example

Motivation

Thrown Exceptions

Constructor & Destructor Documentation

Member Function Documentation

template<class M>
class casacore::TableMeasDesc< M >