uk.ac.starlink.table.join

Class IsotropicCartesianMatchEngine

java.lang.Object

uk.ac.starlink.table.join.AbstractCartesianMatchEngine

uk.ac.starlink.table.join.IsotropicCartesianMatchEngine

All Implemented Interfaces:

MatchEngine

public class IsotropicCartesianMatchEngine
extends AbstractCartesianMatchEngine

Matcher which matches in an isotropic N-dimensional Cartesian space. Two points are considered matching if they fall within a given error distance of each other. The isotropic scale is used as the error.

Since:

25 Aug 2004

Author:

Mark Taylor (Starlink)

Constructor Summary

Constructors

Constructor and Description
IsotropicCartesianMatchEngine(int ndim, double err, boolean normaliseScores) Constructs a matcher which matches points in an ndim-dimensional Cartesian space.

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.
double	getError() Returns the matching error.
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.
ValueInfo[]	getTupleInfos() Returns a set of ValueInfo objects indicating what is required for the elements of each tuple.
void	setError(double err) Sets the matching error.
String	toString()

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

getBinFactor, getIsotropicScale, getNdim, getScale, getTuningParameters, setBinFactor, setIsotropicScale, setScale

Methods inherited from class java.lang.Object

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

Constructor Detail

IsotropicCartesianMatchEngine

public IsotropicCartesianMatchEngine(int ndim,
                                     double err,
                                     boolean normaliseScores)

Constructs a matcher which matches points in an ndim-dimensional Cartesian space. An initial isotropic error margin is specified.

Parameters:

ndim - dimensionality of the space

err - initial maximum distance between two matching points

normaliseScores - true iff you want match scores to be normalised

Method Detail

setError

public void setError(double err)

Sets the matching error.

Parameters:

err - maximum match error

getError

public double getError()

Returns the matching error.

Returns:

maximum match error

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

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

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

toString

public String toString()

Specified by:

toString in class AbstractCartesianMatchEngine