Class ErrorCartesianMatchEngine
- java.lang.Object
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- uk.ac.starlink.table.join.AbstractCartesianMatchEngine
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- uk.ac.starlink.table.join.ErrorCartesianMatchEngine
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- All Implemented Interfaces:
MatchEngine
public class ErrorCartesianMatchEngine extends AbstractCartesianMatchEngine
Match Engine which works in an N-dimensional Cartesian space with isotropic per-row errors. Tuples are N+1 element, with the last element being the error radius, so that a match results when the distance between two objects is no greater than the sum of their error radii.- Since:
- 1 Sep 2011
- Author:
- Mark Taylor
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Field Summary
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Fields inherited from interface uk.ac.starlink.table.join.MatchEngine
NO_BINS
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Constructor Summary
Constructors Constructor Description ErrorCartesianMatchEngine(int ndim, double scale)
Constructor.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
canBoundMatch()
Indicates that theMatchEngine.getMatchBounds(uk.ac.starlink.table.join.NdRange[], int)
method can be invoked to provide some sort of useful result.java.lang.Object[]
getBins(java.lang.Object[] tuple)
Returns a set of keys for bins into which possible matches for a given tuple might fall.NdRange
getMatchBounds(NdRange[] inRanges, int index)
Given a range of tuple values, returns a range outside which no match to anything within that range can result.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 theMatchEngine.matchScore(java.lang.Object[], java.lang.Object[])
method.double
getScale()
Returns the distance scale.double
getScoreScale()
Returns unity.ValueInfo[]
getTupleInfos()
Returns a set of ValueInfo objects indicating what is required for the elements of each tuple.double
matchScore(java.lang.Object[] tuple1, java.lang.Object[] tuple2)
Indicates whether two tuples count as matching each other, and if so how closely.void
setScale(double scale)
Sets the distance scale, which should be roughly the average of per-object error distance This is just used in conjunction with the bin factor for tuning.java.lang.String
toString()
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Methods inherited from class uk.ac.starlink.table.join.AbstractCartesianMatchEngine
getBinFactor, getIsotropicScale, getNdim, getRadiusBins, getScale, getScaleBins, getTuningParameters, setBinFactor, setIsotropicScale, setScale
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Method Detail
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setScale
public void setScale(double scale)
Sets the distance scale, which should be roughly the average of per-object error distance This is just used in conjunction with the bin factor for tuning.- Parameters:
scale
- characteristic scale of errors
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getScale
public double getScale()
Returns the distance scale.- Returns:
- characteristic scale of errors
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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
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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 callingDescribedValue.setValue(java.lang.Object)
on the returned objects.- Returns:
- array of described values which influence the match
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getMatchScoreInfo
public ValueInfo getMatchScoreInfo()
Description copied from interface:MatchEngine
Returns a description of the value returned by theMatchEngine.matchScore(java.lang.Object[], java.lang.Object[])
method. The content class should be numeric (though need not beDouble
), and the name, description and units should be descriptive of whatever the physical significance of the value is. If the result ofmatchScore
is not interesting (for instance, if it's always either 0 or -1),null
may be returned.- Returns:
- metadata for the match score results
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toString
public java.lang.String toString()
- Specified by:
toString
in classAbstractCartesianMatchEngine
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matchScore
public double matchScore(java.lang.Object[] tuple1, java.lang.Object[] tuple2)
Description copied from interface:MatchEngine
Indicates whether two tuples count as matching each other, and if so how closely. If tuple1 and tuple2 are considered as a matching pair, then a non-negative value should be returned indicating how close the match is - the higher the number the worse the match, and a return value of zero indicates a 'perfect' match. If the two tuples do not consitute a matching pair, then a negative number (conventionally -1.0) should be returned. This return value can be thought of as (and will often correspond physically with) the distance in some real or notional space between the points represented by the two submitted tuples.If there's no reason to do otherwise, the range 0..1 is recommended for successul matches. However, if the result has some sort of physical meaning (such as a distance in real space) that may be used instead.
- Parameters:
tuple1
- one tupletuple2
- the other tuple- Returns:
- 'distance' between tuple1 and tuple2; 0 is a perfect match, larger values indicate worse matches, negative values indicate no match
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getScoreScale
public double getScoreScale()
Returns unity.- Returns:
- scale of successful match scores, a positive finite number or NaN
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getBins
public java.lang.Object[] getBins(java.lang.Object[] tuple)
Description copied from interface:MatchEngine
Returns a set of keys for bins into which possible matches for a given tuple might fall. The returned objects can be anything, but should have their equals and hashCode methods implemented properly for comparison.- Parameters:
tuple
- tuple- Returns:
- set of bin keys which might be returned by invoking this method on other tuples which count as matches for the submitted tuple
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canBoundMatch
public boolean canBoundMatch()
Description copied from interface:MatchEngine
Indicates that theMatchEngine.getMatchBounds(uk.ac.starlink.table.join.NdRange[], int)
method can be invoked to provide some sort of useful result.- Returns:
- true iff getMatchBounds may provide useful information
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getMatchBounds
public NdRange getMatchBounds(NdRange[] inRanges, int index)
Description copied from interface:MatchEngine
Given a range of tuple values, returns a range outside which no match to anything within that range can result. If the tuples on which this engine works represent some kind of space, the input values and output values specify a hyper-rectangular region of this space. In the common case in which the match criteria are based on proximity in this space up to a certain error, this method should return a rectangle which is like the input one but broadened in each direction by an amount corresponding to the error.Both the input and output rectangles are specified by tuples representing its opposite corners; equivalently, they are the minimum and maximum values of each tuple element. In either the input or output min/max tuples, any element may be null to indicate that no information is available on the bounds of that tuple element (coordinate).
An array of n-dimensional ranges is given, though only one of them (specified by the
index
value) forms the basis for the output range. The other ranges in the input array may in some cases be needed as context in order to do the calculation. If the match error is fixed, only the single input n-d range is needed to work out the single output range. However, if the errors are obtained by looking at the tuples themselves (match errors are per-row) then in general the broadening has to be done using the maximum error of any of the tables involved in the match, not just the one to be broadened. For a long time, I didn't realise this, so versions of this software up to STIL v3.0-14 (Oct 2015) were not correctly broadening these ranges, leading to potentially missed associations near the edge of bounded regions.This method can be used by match algorithms which know in advance the range of coordinates they will match against and wish to reduce workload by not attempting matches which are bound to fail.
For example, a 1-d Cartesian match engine with an isotropic match error 0.5 would turn input values of ((0,200),(10,210)) into output values ((-0.5,199.5),(10.5,210.5)).
This method will only be called if
MatchEngine.canBoundMatch()
returns true. Thus engines that cannot provide any useful information along these lines (for instance because none of its tuple elements isComparable
) do not need to implement it in a meaningful way.- Parameters:
inRanges
- array of input ranges for the tables on which the match will take place; each element bounds the values for each tuple element in its corresponding table in a possible match (to put it another way - each element gives the coordinates of the opposite corners of a tuple-space rectangle covered by one input table)index
- which element of theinRanges
array for which the broadened output value is required- Returns:
- output range, effectively
inRanges[index]
broadened by errors - See Also:
MatchEngine.canBoundMatch()
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