casa
5.7.0-16
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A class for defining Quantum columns in Tables. More...
#include <TableQuantumDesc.h>
Public Member Functions | |
TableQuantumDesc (const TableDesc &td, const String &column) | |
Constructs a Quantum column descriptor with null units (Unit == ""). More... | |
TableQuantumDesc (const TableDesc &td, const String &column, const Unit &) | |
Constructs a Quantum column descriptor with the specified Quantum unit. More... | |
TableQuantumDesc (const TableDesc &td, const String &column, const Vector< String > &unitNames) | |
Constructs a Quantum column descriptor with the specified Quantum units. More... | |
TableQuantumDesc (const TableDesc &td, const String &column, const Vector< Unit > &) | |
TableQuantumDesc (const TableDesc &td, const String &column, const String &unitCol) | |
Constructs a Quantum column descriptor with variable units stored in unitCol. More... | |
TableQuantumDesc (const TableDesc &td, const String &column, const Char *unitCol) | |
TableQuantumDesc (const TableQuantumDesc &that) | |
Copy constructor (copy semantics). More... | |
~TableQuantumDesc () | |
TableQuantumDesc & | operator= (const TableQuantumDesc &that) |
Assignment. More... | |
const Vector< String > & | getUnits () const |
Returns the Quantum column descriptor's units. More... | |
Bool | isUnitVariable () const |
Returns True if descriptor set for variable units (one per row) More... | |
const String & | columnName () const |
Returns the name of the quantum column. More... | |
const String & | unitColumnName () const |
Returns the name of the units column (an empty String is returned if the units are not variable). More... | |
void | write (TableDesc &) |
Makes the TableQuantumDesc persistent (updates the Table Descriptor). More... | |
void | write (Table &) |
Static Public Member Functions | |
static TableQuantumDesc * | reconstruct (const TableDesc &td, const String &column) |
Reconstructs a previously constructed TableQuantumDesc. More... | |
static Bool | hasQuanta (const TableColumn &column) |
Does this column contain table quanta? More... | |
Private Member Functions | |
void | writeKeys (TableRecord &columnKeyset) |
Write the actual keywords. More... | |
void | checkColumn (const TableDesc &td) const |
Throw an exception if the quantum column doesn't exist. More... | |
void | checkUnitsColumn (const TableDesc &td) const |
Throw an exception if the variable units column isn't a string column. More... | |
Private Attributes | |
String | itsColName |
Name of column which stores the Quantum's values. More... | |
Vector< String > | itsUnitsName |
The Quantum's unit as a string. More... | |
String | itsUnitsColName |
Name of units column if units are variable. More... | |
A class for defining Quantum columns in Tables.
Public interface
A TableQuantumDesc object is used to define a Quantum column in a Table. The use of this object and the associated Scalar- and ArrayQuantColumn objects make it possible to store (and retrieve) Quanta in Tables.
TableQuantumDesc objects are analogous to ColumnDesc objects in that they add information, describing the characteristics of a column, to the Table Descriptor before the Table is created. However, rather than replacing the use of a ColumnDesc object, a TableQuantumDesc is used in conjunction with a ColumnDesc in the definition of Quantum columns.
Caution: A good understanding of the Table system is essential before attempting to use this class;
Defining a Quantum column requires the following steps:
It is also possible to define a Quantum column after the table is created. which is useful when columns (to be used for quanta) are added to an already existing table.
The type of the quantum columns must match the type of the underlying Quanta that are to be stored in the column. Hence, for a column of Quantum<Complex> a ScalarColumnDesc<Complex> must be used.
As with standard Table Columns Quanta can be stored in Scalar and Array columns. This must be specified in advance by using either a Scalar- or ArrayColumnDesc.
After the Table has be created a Quantum column can be accessed for writing and reading of Quanta via the (RO)ScalarQuantColumn<T> and (RO)ArrayQuantColumn<T> objects.
The treatment of the Unit component of a Quantum in the TableQuantumDesc class varies depending on your needs. The main consideration is whether the Quanta to be stored in a specific column are to have the same Unit or whether their Units could differ. In the simple case, where the Quanta have the same unit, a TableQuantumDesc is declared with the Unit value specified as a parameter. The following defines a Quantum column with units "deg":
This constructor stores the value for the Unit as a column keyword. In situations, however, where it is necessary to store a distinct Unit with each Quantum, it is necessary to define an additional column for storing the Unit component of each Quantum. The TableQuantumDesc constructor for this takes the name of the Unit column as a parameter. Hence an additional column must be defined for storing the Units and its type must be string. The following example shows how to set up a Quantum column with support for Quantum unit variability:
One further consideration is that for Array Quantum Columns it is necessary to decide on a level of granularity for the Unit storage you would like. In Array Quantum columns it is possible to store a distinct Unit per row or per array element per row. This distinction is established when the Unit column is declared. Defining a ScalarColumn for Units specifies per row variability, that is, each row in an array column of Quanta will have the same unit. Alternatively, use of an ArrayColumn for the Unit column specifies that every Quantum stored will have its unit stored as well. In both cases the Unit column's type must be String. The following defines an Array Quantum Column with per row Unit storage:
And finally, an array Quantum Column with an Array Unit Column:
After constructing an TableQuantumDesc object use of the write() member updates the Table Descriptor or Table object. (RO)ScalarQuantColumn<T> and (RO)ArrayQuantColumn<T> are subsequently used to read-only and read/write access the Quantum Columns.
Note that writing the Quantum description could also be done after the table is created. It is meaningless in this case, but it is useful when columns (to be used for quanta) are added to an already existing table. be used as
This class assists in the definition of a Quantum Table Column.
Definition at line 265 of file TableQuantumDesc.h.
casacore::TableQuantumDesc::TableQuantumDesc | ( | const TableDesc & | td, |
const String & | column, | ||
const Vector< Unit > & | |||
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casacore::TableQuantumDesc::TableQuantumDesc | ( | const TableDesc & | td, |
const String & | column, | ||
const Char * | unitCol | ||
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casacore::TableQuantumDesc::TableQuantumDesc | ( | const TableQuantumDesc & | that | ) |
Copy constructor (copy semantics).
casacore::TableQuantumDesc::~TableQuantumDesc | ( | ) |
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Throw an exception if the quantum column doesn't exist.
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Throw an exception if the variable units column isn't a string column.
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inline |
Returns the name of the quantum column.
Definition at line 323 of file TableQuantumDesc.h.
References itsColName.
Returns the Quantum column descriptor's units.
A empty vector is returned if units have not been specified. This could be because the null unit constructor was used or because the units are variable.
Definition at line 315 of file TableQuantumDesc.h.
References itsUnitsName.
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Does this column contain table quanta?
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Returns True if descriptor set for variable units (one per row)
Definition at line 319 of file TableQuantumDesc.h.
References casacore::String::empty(), and itsUnitsColName.
TableQuantumDesc& casacore::TableQuantumDesc::operator= | ( | const TableQuantumDesc & | that | ) |
Assignment.
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Reconstructs a previously constructed TableQuantumDesc.
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Returns the name of the units column (an empty String is returned if the units are not variable).
Definition at line 328 of file TableQuantumDesc.h.
References itsUnitsColName.
void casacore::TableQuantumDesc::write | ( | TableDesc & | ) |
Makes the TableQuantumDesc persistent (updates the Table Descriptor).
void casacore::TableQuantumDesc::write | ( | Table & | ) |
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private |
Write the actual keywords.
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Name of column which stores the Quantum's values.
Definition at line 342 of file TableQuantumDesc.h.
Referenced by columnName().
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Name of units column if units are variable.
Definition at line 346 of file TableQuantumDesc.h.
Referenced by isUnitVariable(), and unitColumnName().
The Quantum's unit as a string.
Definition at line 344 of file TableQuantumDesc.h.
Referenced by getUnits().