de.lmu.ifi.dbs.elki.distance.distancefunction.external

Class FileBasedDoubleDistanceFunction

java.lang.Object

de.lmu.ifi.dbs.elki.distance.distancefunction.AbstractDBIDDistanceFunction<DoubleDistance>

de.lmu.ifi.dbs.elki.distance.distancefunction.external.FileBasedDoubleDistanceFunction

All Implemented Interfaces:

DBIDDistanceFunction<DoubleDistance>, DistanceFunction<DBID,DoubleDistance>, Parameterizable

@Title(value="File based double distance for database objects.")
@Description(value="Loads double distance values from an external text file.")
public class FileBasedDoubleDistanceFunction
extends AbstractDBIDDistanceFunction<DoubleDistance>

Provides a DistanceFunction that is based on double distances given by a distance matrix of an external file. See NumberDistanceParser for the default input format.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FileBasedDoubleDistanceFunction.Parameterizer Parameterization class.

Field Summary

Fields

Modifier and Type	Field and Description
private Map<DBIDPair,DoubleDistance>	cache The distance cache
static OptionID	MATRIX_ID Parameter that specifies the name of the distance matrix file.
static OptionID	PARSER_ID Optional parameter to specify the parsers to provide a database, must extend DistanceParser.

Constructor Summary

Constructors

Constructor and Description
FileBasedDoubleDistanceFunction(DistanceParser<DoubleDistance> parser, File matrixfile) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
DoubleDistance	distance(DBIDRef id1, DBIDRef id2) Returns the distance between the two objects specified by their objects ids.
boolean	equals(Object obj)
DoubleDistance	getDistanceFactory() Method to get the distance functions factory.
private void	loadCache(DistanceParser<DoubleDistance> parser, File matrixfile)

Methods inherited from class de.lmu.ifi.dbs.elki.distance.distancefunction.AbstractDBIDDistanceFunction

getInputTypeRestriction, instantiate, isMetric, isSymmetric

Methods inherited from class java.lang.Object

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

Field Detail

MATRIX_ID

public static final OptionID MATRIX_ID

Parameter that specifies the name of the distance matrix file.

Key: -distance.matrix

PARSER_ID

public static final OptionID PARSER_ID

Optional parameter to specify the parsers to provide a database, must extend DistanceParser. If this parameter is not set, NumberDistanceParser is used as parser for all input files.

Key: -distance.parser

cache

private Map<DBIDPair,DoubleDistance> cache

The distance cache

Constructor Detail

FileBasedDoubleDistanceFunction

public FileBasedDoubleDistanceFunction(DistanceParser<DoubleDistance> parser,
                               File matrixfile)

Constructor.

Parameters:

parser - Parser

matrixfile - input file

Method Detail

distance

public DoubleDistance distance(DBIDRef id1,
                      DBIDRef id2)

Returns the distance between the two objects specified by their objects ids. If a cache is used, the distance value is looked up in the cache. If the distance does not yet exists in cache, it will be computed an put to cache. If no cache is used, the distance is computed.

Specified by:

distance in interface DBIDDistanceFunction<DoubleDistance>

Specified by:

distance in class AbstractDBIDDistanceFunction<DoubleDistance>

Parameters:

id1 - first object id

id2 - second object id

Returns:

the distance between the two objects specified by their objects ids

loadCache

private void loadCache(DistanceParser<DoubleDistance> parser,
             File matrixfile)
                throws IOException

Throws:

IOException

getDistanceFactory

public DoubleDistance getDistanceFactory()

Description copied from interface: DistanceFunction

Method to get the distance functions factory.

Specified by:

getDistanceFactory in interface DistanceFunction<DBID,DoubleDistance>

Specified by:

getDistanceFactory in class AbstractDBIDDistanceFunction<DoubleDistance>

Returns:

Factory for distance objects

equals

public boolean equals(Object obj)

Overrides:

equals in class Object