uk.ac.starlink.table.join

Class FixedSkyMatchEngine

java.lang.Object

uk.ac.starlink.table.join.AbstractSkyMatchEngine

uk.ac.starlink.table.join.FixedSkyMatchEngine

All Implemented Interfaces:

MatchEngine

Direct Known Subclasses:

FixedSkyMatchEngine.InDegrees

public class FixedSkyMatchEngine
extends AbstractSkyMatchEngine

MatchEngine which matches objects on the celestial sphere with a fixed maximum separation. The tuples it uses are two-element arrays of Number objects, representing Right Ascension and Declination respectively in radians. Other similar longitude/latitude-like coordinate systems may alternatively be used.

Since:

6 Sep 2011

Author:

Mark Taylor

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FixedSkyMatchEngine.InDegrees MatchEngine class that behaves like FixedSkyMatchEngine but uses human-friendly units (degrees and arcseconds) rather than radians for tuple elements and match parameters.

Constructor Summary

Constructors

Constructor and Description
FixedSkyMatchEngine(SkyPixellator pixellator, double separation) Constructor.

Method Summary

Modifier and Type	Method and Description
java.util.function.Supplier<Coverage>	createCoverageFactory() Returns a supplier for coverage objects.
java.util.function.Supplier<MatchKit>	createMatchKitFactory() Returns a factory for MatchKit instances corresponding to the current settings of this object.
DescribedValue[]	getMatchParameters() Returns a set of DescribedValue objects whose values can be modified to modify the matching criteria.
ValueInfo	getMatchScoreInfo() Returns a description of the value returned by the MatchKit.matchScore(java.lang.Object[], java.lang.Object[]) method.
double	getScoreScale() Returns a scale value for the match score.
double	getSeparation() Returns the maximum separation which corresponds to a match.
ValueInfo[]	getTupleInfos() Returns a set of ValueInfo objects indicating what is required for the elements of each tuple.
void	setSeparation(double separation) Sets the maximum separation which corresponds to a match.
String	toString()

Methods inherited from class uk.ac.starlink.table.join.AbstractSkyMatchEngine

calculateSeparation, getPixellator, getScale, getTuningParameters, isSkyPosition, setScale

Methods inherited from class java.lang.Object

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

Constructor Detail

FixedSkyMatchEngine

public FixedSkyMatchEngine(SkyPixellator pixellator,
                           double separation)

Constructor.

Parameters:

pixellator - handles sky pixellisation

separation - initial value for maximum match separation, in radians

Method Detail

setSeparation

public void setSeparation(double separation)

Sets the maximum separation which corresponds to a match.

Parameters:

separation - maximum separation in radians

getSeparation

public double getSeparation()

Returns the maximum separation which corresponds to a match.

Returns:

maximum separation in radians

getTupleInfos

public ValueInfo[] getTupleInfos()

Description copied from interface: MatchEngine

Returns a set of ValueInfo objects indicating what is required for the elements of each tuple. The length of this array is the number of elements in the tuple. Each element should at least have a defined name and content class. The info's nullable attribute has a special meaning: if true it means that it makes sense for this element of the tuple to be always blank (for instance assigned to no column).

Returns:

array of objects describing the requirements on each element of the tuples used for matching

getMatchParameters

public DescribedValue[] getMatchParameters()

Description copied from interface: MatchEngine

Returns a set of DescribedValue objects whose values can be modified to modify the matching criteria. Typically at least one of these will be some sort of tolerance separation which determines how close tuples must be to count as a match. This match engine's behaviour can be modified by calling DescribedValue.setValue(java.lang.Object) on the returned objects.

Returns:

array of described values which influence the match

getMatchScoreInfo

public ValueInfo getMatchScoreInfo()

Description copied from interface: MatchEngine

Returns a description of the value returned by the MatchKit.matchScore(java.lang.Object[], java.lang.Object[]) method. The content class should be numeric (though need not be Double), and the name, description and units should be descriptive of whatever the physical significance of the value is. If the result of matchScore is not interesting (for instance, if it's always either 0 or -1), null may be returned.

Returns:

metadata for the match score results

createMatchKitFactory

public java.util.function.Supplier<MatchKit> createMatchKitFactory()

Description copied from interface: MatchEngine

Returns a factory for MatchKit instances corresponding to the current settings of this object.

The returned value is immutable, and is not affected by subsequent changes of the settings of this object.

Returns:

match kit supplier

createCoverageFactory

public java.util.function.Supplier<Coverage> createCoverageFactory()

Description copied from interface: MatchEngine

Returns a supplier for coverage objects. Each such coverage can be used to characterise a region of tuple space. When populated with a set of tuples A, any tuple for which the inclusion function defined by its Coverage.createTestFactory() method returns false is guaranteed not to match any tuple in A according to this object's match criteria.

The returned value is immutable, and is not affected by subsequent changes of the settings of this object.

If no suitable implementation is available, null may be returned.

Returns:

supplier of coverage objects, or null

getScoreScale

public double getScoreScale()

Description copied from interface: MatchEngine

Returns a scale value for the match score. The intention is that the result of matchScore/MatchEngine.getScoreScale() is of order unity, and is thus comparable between different match engines.

As a general rule, the result should be the maximum value ever returned from the matchScore method, corresponding to the least good successful match. For binary MatchEngine implementations (all matches are either score=0 or failures) a value of 1 is recommended. If nothing reliable can be said about the scale, NaN may be returned.

Returns:

scale of successful match scores, a positive finite number or NaN

toString

public String toString()

Specified by:

toString in class AbstractSkyMatchEngine