uk.ac.starlink.topcat
Class SyntheticRowSubset

java.lang.Object
  uk.ac.starlink.topcat.RowSubset
      uk.ac.starlink.topcat.SyntheticRowSubset

public class SyntheticRowSubset
extends RowSubset

A RowSubset which uses an algebraic expression based on the values of other columns in the same row to decide whether a row is included or not.

The engine used for expression evaluation is the GNU Java Expressions Library (JEL).

Author:

Mark Taylor (Starlink)

See Also:

JEL

Field Summary

Fields inherited from class uk.ac.starlink.topcat.RowSubset

ALL, NONE

Constructor Summary

SyntheticRowSubset(String name, String expression, uk.ac.starlink.ttools.jel.RandomJELRowReader rowReader)
Constructs a new synthetic subset given a table and an algebraic expression.

Method Summary

String	getExpression() Returns the text of the expression used by this subset.
boolean	isIncluded(long lrow) Indicates whether a given row is in the subset or not.
void	setExpression(String expression, uk.ac.starlink.ttools.jel.RandomJELRowReader rowReader) Sets the expression to use for this subset.

Methods inherited from class uk.ac.starlink.topcat.RowSubset

getName, setName, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

SyntheticRowSubset

public SyntheticRowSubset(String name,
                          String expression,
                          uk.ac.starlink.ttools.jel.RandomJELRowReader rowReader)
                   throws gnu.jel.CompilationException

Constructs a new synthetic subset given a table and an algebraic expression.

Parameters:

name - the name to use for the new RowSubset

expression - the algebraic expression

rowReader - context for JEL expression evaluation

Throws:

gnu.jel.CompilationException

Method Detail

setExpression

public void setExpression(String expression,
                          uk.ac.starlink.ttools.jel.RandomJELRowReader rowReader)
                   throws gnu.jel.CompilationException

Sets the expression to use for this subset.

Parameters:

expression - JEL expression

rowReader - context for JEL expression evaluation

Throws:

gnu.jel.CompilationException

getExpression

public String getExpression()

Returns the text of the expression used by this subset.

Returns:

expression

isIncluded

public boolean isIncluded(long lrow)

Description copied from class: RowSubset

Indicates whether a given row is in the subset or not.

Specified by:

isIncluded in class RowSubset

Parameters:

lrow - the index of the row in question

Returns:

true iff row lrow is to be included