org.terrier.matching.models

Class WeightingModelLibrary

java.lang.Object

org.terrier.matching.models.WeightingModelLibrary

public class WeightingModelLibrary
extends Object

A library of tf normalizations for weighting models such as the pivoted length normalization described in Singhal et al., 1996.

Since:

4.0

Author:

Francois Rousseau

Field Summary

Fields

Modifier and Type	Field and Description
static double	LOG_2_OF_E The logarithm in base 2 of e, used to change the base of logarithms.
static double	LOG_E_OF_2 The natural logarithm of 2, used to change the base of logarithms.

Constructor Summary

Constructors

Constructor and Description
WeightingModelLibrary()

Method Summary

Methods

Modifier and Type	Method and Description
static double	log(double d) Returns the base 2 log of the given double precision number.
static double	log(double d1, double d2) Returns the base 2 log of d1 over d2
static double	relativeFrequency(double tf, double docLength) Computes relative term frequency.
static double	stirlingPower(double n, double m) This method provides the contract for implementing the Stirling formula for the power series.
static double	tf_concave_k(double tf, double k) Returns a concave tf as described in Robertson and Walker, 1994.
static double	tf_concave_log(double tf) Returns a concave tf as described in Singhal et al., 1999.
static double	tf_cornell(double tf, double s, double dl, double avdl) Returns a concave pivot length normalized tf as described in Singhal et al., 1999.
static double	tf_pivoted(double tf, double slope, double dl, double avdl) Returns a modified tf with pivot length normalization as described in Singhal et al., 1996.
static double	tf_robertson(double tf, double b, double dl, double avdl, double k1) Returns a concave pivot length normalized tf as described in Robertson et al., 1999.

Methods inherited from class java.lang.Object

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

Field Detail

LOG_E_OF_2

public static final double LOG_E_OF_2

The natural logarithm of 2, used to change the base of logarithms.

LOG_2_OF_E

public static final double LOG_2_OF_E

The logarithm in base 2 of e, used to change the base of logarithms.

Constructor Detail

WeightingModelLibrary

public WeightingModelLibrary()

Method Detail

log

public static double log(double d)

Returns the base 2 log of the given double precision number.

Parameters:

d - The number of which the log we will compute

Returns:

the base 2 log of the given number

log

public static double log(double d1,
         double d2)

Returns the base 2 log of d1 over d2

Parameters:

d1 - the numerator

d2 - the denominator

Returns:

the base 2 log of d1/d2

tf_pivoted

public static double tf_pivoted(double tf,
                double slope,
                double dl,
                double avdl)

Returns a modified tf with pivot length normalization as described in Singhal et al., 1996. Pivoted document length normalization (SIGIR '96), pages 21-29.

Parameters:

tf - the term frequency to modify

slope - the slope

dl - the document length

avdl - the average document length in the collection

Returns:

a pivot length normalized tf

tf_concave_k

public static double tf_concave_k(double tf,
                  double k)

Returns a concave tf as described in Robertson and Walker, 1994. Some simple effective approximations to the 2-poisson model for probabilistic weighted retrieval (SIGIR '94), page 232-241.

Parameters:

tf - the term frequency to modify

k - the concavity coefficient

Returns:

a concave tf

tf_concave_log

public static double tf_concave_log(double tf)

Returns a concave tf as described in Singhal et al., 1999. AT&T at TREC-7. In Proceedings of the Seventh Text REtrieval Conference (TREC-7), pages 239-252.

Parameters:

tf - the term frequency to modify

Returns:

a concave tf

relativeFrequency

public static final double relativeFrequency(double tf,
                       double docLength)

Computes relative term frequency. When tf == docLength we return 0.99999 because relative frequency of 1 produces Not a Number (NaN) or Negative Infinity as scores in hyper-geometric models (DPH, DLH and DLH13).

Parameters:

tf - raw term frequency

docLength - length of the document

Returns:

relative term frequency

tf_robertson

public static double tf_robertson(double tf,
                  double b,
                  double dl,
                  double avdl,
                  double k1)

Returns a concave pivot length normalized tf as described in Robertson et al., 1999. Okapi at TREC-7: automatic ad hoc, filtering, VLC and filtering tracks. In Proceedings of the Seventh Text REtrieval Conference (TREC-7), pages 253-264

Parameters:

tf - the term frequency to modify

b - the slope

dl - the document length

avdl - the average document length in the collection

k1 - the concavity coefficient

Returns:

a concave pivot length normalized tf

tf_cornell

public static double tf_cornell(double tf,
                double s,
                double dl,
                double avdl)

Returns a concave pivot length normalized tf as described in Singhal et al., 1999. AT&T at TREC-7. In Proceedings of the Seventh Text REtrieval Conference (TREC-7), pages 239-252.

Parameters:

tf - the term frequency to modify

s - the slope

dl - the document length

avdl - the average document length in the collection

Returns:

a concave pivot length normalized tf

stirlingPower

public static double stirlingPower(double n,
                   double m)

This method provides the contract for implementing the Stirling formula for the power series.

Parameters:

n - The parameter of the Stirling formula.

m - The parameter of the Stirling formula.

Returns:

the approximation of the power series