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

Nested Class Summary

Nested classes/interfaces inherited from class uk.ac.starlink.topcat.RowSubset

RowSubset.Key

Field Summary

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

ALL, NONE

Constructor Summary

Constructors

Constructor and Description
SyntheticRowSubset(String name, TopcatModel tcModel, String expression) Constructs a new synthetic subset given a table and an algebraic expression.

Method Summary

Modifier and Type	Method and Description
String	getExpression() Returns the text of the expression used by this subset.
String	getMaskId() Returns the mask identifier by which the content of this subset is recognised.
boolean	isIncluded(long lrow) Indicates whether a given row is in the subset or not.
void	setExpression(String expression) Sets the expression to use for this subset.

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

getKey, getName, setKey, 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,
                          TopcatModel tcModel,
                          String expression)
                   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

tcModel - context for JEL expression evaluation

expression - the algebraic expression

Throws:

gnu.jel.CompilationException

Method Detail

setExpression

public void setExpression(String expression)
                   throws gnu.jel.CompilationException

Sets the expression to use for this subset.

Parameters:

expression - JEL expression

Throws:

gnu.jel.CompilationException

getExpression

public String getExpression()

Returns the text of the expression used by this subset.

Returns:

expression

getMaskId

public String getMaskId()

Description copied from class: RowSubset

Returns the mask identifier by which the content of this subset is recognised.

In particular this value is used as a maskId by the GuiDataSpec class, which means that changing it will generally signal to the plotting system that the content of this subset has changed, and thus provoke a replot of layers dependent on it.

The default implementation returns a value determined by the identity of this RowSubset object (TopcatUtils.identityString(java.lang.Object)), but this method may be overridden by subclasses that wish to signal their changes, and in particular provoke replots, according to state. Implementations are not however obliged to make this value reflect their internal state, especially if it would be expensive to do so. Implementations should be fast.

Overrides:

getMaskId in class RowSubset

Returns:

mask content identifier

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