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java.lang.Objectuk.ac.starlink.table.join.SkyMatchEngine
public abstract class SkyMatchEngine
Abstract superclass for match engines which match positions on the sky.
The tuples it uses are two-element arrays of Number
objects, the first giving Right Ascension in radians, and the second
giving Declination in radians.
The separation attribute indicates how many radians may
separate two points on the celestial sphere for them to be
considered matching.
Field Summary |
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Fields inherited from interface uk.ac.starlink.table.join.MatchEngine |
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NO_BINS |
Constructor Summary | |
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SkyMatchEngine(boolean useErrors)
Constructs a new match engine which considers two points (RA,Dec tuples) to match if they are within a given angular distance on the celestial sphere. |
Method Summary | |
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static double |
calculateSeparation(double ra1,
double dec1,
double ra2,
double dec2)
Returns the distance along a great circle between two points. |
boolean |
canBoundMatch()
Indicates that the MatchEngine.getMatchBounds(java.lang.Comparable[], java.lang.Comparable[]) method can be invoked
to provide some sort of useful result. |
protected abstract java.lang.Object[] |
getBins(double ra,
double dec,
double err)
Returns a set of keys for bins into which possible matches for a given sky position, with a given error, might fall. |
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. |
java.lang.Comparable[][] |
getMatchBounds(java.lang.Comparable[] radecMinIn,
java.lang.Comparable[] radecMaxIn)
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 the MatchEngine.matchScore(java.lang.Object[], java.lang.Object[]) method. |
double |
getSeparation()
Returns the separation between points within which they will be considered to match. |
ValueInfo[] |
getTupleInfos()
Returns a set of ValueInfo objects indicating what is required for the elements of each tuple. |
boolean |
getUseErrors()
Indicates whether this engine is using per-row errors for matching. |
double |
matchScore(java.lang.Object[] tuple1,
java.lang.Object[] tuple2)
Determines the match score of two tuples. |
void |
setSeparation(double separation)
Configures this match engine to consider two points (RA,Dec tuples) to match if they are within a given angular distance on the celestial sphere. |
void |
setUseErrors(boolean use)
Sets whether this engine will use per-row errors for matching. |
java.lang.String |
toString()
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Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Methods inherited from interface uk.ac.starlink.table.join.MatchEngine |
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getTuningParameters |
Constructor Detail |
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public SkyMatchEngine(boolean useErrors)
useErrors
- if true, per-row errors can be specified as
a third element of the tuples; otherwise only the fixed
separation value countsMethod Detail |
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public void setSeparation(double separation)
separation
- match radius in radianspublic double getSeparation()
public boolean getUseErrors()
public void setUseErrors(boolean use)
use
- true to use per-row errorspublic double matchScore(java.lang.Object[] tuple1, java.lang.Object[] tuple2)
useErrors
is true the tuples are three-element,
giving RA, Dec and error radius, all as Number objects in radians.
If it is false, they are two element, giving just RA and Dec.
matchScore
in interface MatchEngine
tuple1
- values representing first pointtuple2
- values representing second point
public java.lang.Object[] getBins(java.lang.Object[] tuple)
MatchEngine
getBins
in interface MatchEngine
tuple
- tuple
protected abstract java.lang.Object[] getBins(double ra, double dec, double err)
equals
and hashCode
methods
implemented properly for comparison.
The err
value will not be greater than the current
result of getSeparation
.
ra
- right ascension of point to test (radians)dec
- declination of point to test (radians)err
- possible distance away from given location of matchgetBins(java.lang.Object[])
public ValueInfo getMatchScoreInfo()
MatchEngine
MatchEngine.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.
getMatchScoreInfo
in interface MatchEngine
public ValueInfo[] getTupleInfos()
MatchEngine
getTupleInfos
in interface MatchEngine
public DescribedValue[] getMatchParameters()
MatchEngine
DescribedValue.setValue(java.lang.Object)
on the
returned objects.
getMatchParameters
in interface MatchEngine
public java.lang.String toString()
toString
in class java.lang.Object
public boolean canBoundMatch()
MatchEngine
MatchEngine.getMatchBounds(java.lang.Comparable[], java.lang.Comparable[])
method can be invoked
to provide some sort of useful result.
canBoundMatch
in interface MatchEngine
public java.lang.Comparable[][] getMatchBounds(java.lang.Comparable[] radecMinIn, java.lang.Comparable[] radecMaxIn)
MatchEngine
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).
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 is Comparable
do not need to
implement it in a meaningful way.
getMatchBounds
in interface MatchEngine
radecMinIn
- tuple consisting of the minimum values of each
tuple element in a possible match
(to put it another way - coordinates of one corner of a
tuple-space rectangle containing such a match)radecMaxIn
- tuple consisting of the maximum values of each
tuple element in a possible match
(to put it another way - coordinates of the other corner of a
tuple-space rectangle containing such a match)
MatchEngine.canBoundMatch()
public static double calculateSeparation(double ra1, double dec1, double ra2, double dec2)
ra1
- right ascension of point 1 in radiansdec1
- declination of point 1 in radiansra2
- right ascension of point 2 in radiansdec2
- declination of point 2 in radians
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Copyright © 2004 CLRC: Central Laboratory of the Research Councils. All rights reserved. | ||||||||
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