org.terrier.matching.models

Class Idf

java.lang.Object

org.terrier.matching.models.Idf

All Implemented Interfaces:

Serializable, Cloneable

public final class Idf
extends Object
implements Serializable, Cloneable

This class computes the idf values for specific terms in the collection.

Author:

Gianni Amati, Ben He, Vassilis Plachouras

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static double	LOG_E_OF_2 Deprecated.
static double	REC_LOG_2_OF_E Deprecated.

Constructor Summary

Constructors

Constructor and Description
Idf() A default constructor.
Idf(double docs) A constructor specifying the number of documents in the collection.

Method Summary

Methods

Modifier and Type	Method and Description
Object	clone() Make a perfect clone of this object
double	idf(double d) Returns the idf of d.
double	idf(int d) Returns the idf of the given number d.
double	idfDFR(double d) Returns the idf of d.
double	idfDFR(int d) Returns the idf of the given number d.
double	idfENQUIRY(double d) The INQUERY idf formula.
double	idfN(double d) Return the normalised idf of the given number.
double	idfN(int d) Return the normalised idf of the given number.
double	idfNENQUIRY(double d) The normalised INQUERY idf formula
static double	log(double d) Deprecated.
static double	log(double d1, double d2) Deprecated.
static void	main(String[] args) main
void	setNumberOfDocuments(double N) Set number of documents

Methods inherited from class java.lang.Object

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

Field Detail

LOG_E_OF_2

@Deprecated
public static final double LOG_E_OF_2

Deprecated.

The natural logarithm of 2, used to change the base of logarithms. Do not use, moved to WeightingModelLibrary

REC_LOG_2_OF_E

@Deprecated
public static final double REC_LOG_2_OF_E

Deprecated.

The logarithm in base 2 of e, used to change the base of logarithms. Do not use, moved to WeightingModelLibrary

Constructor Detail

Idf

public Idf()

A default constructor. NOTE: You must set the number of documents if you intend to use the idf* functions in this class

Idf

public Idf(double docs)

A constructor specifying the number of documents in the collection.

Parameters:

docs - The number of documents.

Method Detail

clone

public Object clone()

Make a perfect clone of this object

Overrides:

clone in class Object

idf

public double idf(double d)

Returns the idf of d.

Parameters:

d - The given term frequency

Returns:

the base 2 log of numberOfDocuments/d

idf

public double idf(int d)

Returns the idf of the given number d.

Parameters:

d - the number for which the idf will be computed.

Returns:

the idf of the given number d.

idfDFR

public double idfDFR(double d)

Returns the idf of d.

Parameters:

d - The given term frequency

Returns:

the base 2 log of numberOfDocuments/d

idfDFR

public double idfDFR(int d)

Returns the idf of the given number d.

Parameters:

d - the number for which the idf will be computed.

Returns:

the idf of the given number d.

idfENQUIRY

public double idfENQUIRY(double d)

The INQUERY idf formula. We need to check again this formula, as it seems that there is a bug in the expression numberOfDocuments - d / d.

Parameters:

d - the number for which the idf will be computed

Returns:

the INQUERY idf of the number d

idfN

public double idfN(double d)

Return the normalised idf of the given number.

Parameters:

d - The number of which the idf is computed.

Returns:

the normalised idf of d

setNumberOfDocuments

public void setNumberOfDocuments(double N)

Set number of documents

Parameters:

N - the number of ducuments

idfN

public double idfN(int d)

Return the normalised idf of the given number.

Parameters:

d - The number of which the idf is computed.

Returns:

the normalised idf of d

idfNENQUIRY

public double idfNENQUIRY(double d)

The normalised INQUERY idf formula

Parameters:

d - the number for which we will compute the normalised idf

Returns:

the normalised INQUERY idf of d

main

public static void main(String[] args)

main

Parameters:

args -

log

@Deprecated
public static double log(double d)

Deprecated.

Returns the base 2 log of the given double precision number. Method has been moved to WeightingModelLibrary

Parameters:

d - The number of which the log we will compute

Returns:

the base 2 log of the given numbers

log

@Deprecated
public static double log(double d1,
                    double d2)

Deprecated.

Returns the base 2 log of d1 over d2. Do not use, moved to WeightingModelLibrary

Parameters:

d1 - the numerator

d2 - the denominator

Returns:

the base 2 log of d1/d2