uk.ac.starlink.ttools.filter

Class JELColumnSupplement

java.lang.Object

uk.ac.starlink.ttools.filter.JELColumnSupplement

All Implemented Interfaces:

ColumnSupplement

public class JELColumnSupplement
extends Object
implements ColumnSupplement

ColumnSupplement that generates new columns based on JEL expressions.

Since:

27 Mar 2012

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
JELColumnSupplement(StarTable inTable, String[] exprs, ColumnInfo[] colInfos) Constructs a multiple-column JEL column supplement.
JELColumnSupplement(StarTable inTable, String expr, ColumnInfo colInfo) Constructs a single-column JEL column supplement.

Method Summary

Modifier and Type	Method and Description
SupplementData	createSupplementData(RowData rdata) Returns a new accessor for the values in the columns defined by this object.
Object	getCell(long irow, int icol) Random access read of a cell defined by this object.
int	getColumnCount() Returns the number of columns defined by this object.
ColumnInfo	getColumnInfo(int icol) Returns the column metadata object for a given column.
Object[]	getRow(long irow) Random access read of a row defined by this object.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JELColumnSupplement

public JELColumnSupplement(StarTable inTable,
                           String[] exprs,
                           ColumnInfo[] colInfos)
                    throws IOException

Constructs a multiple-column JEL column supplement.

Parameters:

inTable - table providing JEL context

exprs - JEL expressions for columns

colInfos - metadata for columns (data types may be changed to match expression output); if null, names are generated automatically

Throws:

IOException - with a helpful message if one of the expressions cannot be compiled

JELColumnSupplement

public JELColumnSupplement(StarTable inTable,
                           String expr,
                           ColumnInfo colInfo)
                    throws IOException

Constructs a single-column JEL column supplement.

Parameters:

inTable - table providing JEL context

expr - JEL expression for column

colInfo - metadata for column (data type may be changed to match expression output); if null, name is generated automatically

Throws:

IOException

Method Detail

getColumnCount

public int getColumnCount()

Description copied from interface: ColumnSupplement

Returns the number of columns defined by this object.

Specified by:

getColumnCount in interface ColumnSupplement

Returns:

number of columns

getColumnInfo

public ColumnInfo getColumnInfo(int icol)

Description copied from interface: ColumnSupplement

Returns the column metadata object for a given column.

Specified by:

getColumnInfo in interface ColumnSupplement

Parameters:

icol - column index within this object

Returns:

column metadata for the icol'th column defined by this object

getCell

public Object getCell(long irow,
                      int icol)
               throws IOException

Description copied from interface: ColumnSupplement

Random access read of a cell defined by this object.

Specified by:

getCell in interface ColumnSupplement

Parameters:

irow - row index

icol - column index

Returns:

cell content

Throws:

IOException

getRow

public Object[] getRow(long irow)
                throws IOException

Description copied from interface: ColumnSupplement

Random access read of a row defined by this object.

Specified by:

getRow in interface ColumnSupplement

Parameters:

irow - row index

Returns:

array of cell contents for all the cells in this row

Throws:

IOException

createSupplementData

public SupplementData createSupplementData(RowData rdata)
                                    throws IOException

Description copied from interface: ColumnSupplement

Returns a new accessor for the values in the columns defined by this object. The supplied row object must be from an appropriate host table; if not, behaviour is undefined.

Specified by:

createSupplementData in interface ColumnSupplement

Parameters:

rdata - row accessor providing data from the host table

Returns:

accessor over row data from supplementary columns

Throws:

IOException