CDPL.Descr.TverskySimilarity Class Reference

Functor class for calculating the Tversky Similarity [GSIM] of bitsets. More...

Inheritance diagram for CDPL.Descr.TverskySimilarity:

Public Member Functions
None	__init__ (float alpha=0.95, float beta=0.05)
	Constructor. More...
None	__init__ (TverskySimilarity func)
	Initializes a copy of the TverskySimilarity instance func. More...
int	getObjectID ()
	Returns the numeric identifier (ID) of the wrapped C++ class instance. More...
TverskySimilarity	assign (TverskySimilarity func)
	Replaces the current state of self with a copy of the state of the TverskySimilarity instance func. More...
float	__call__ (Util.BitSet bs1, Util.BitSet bs2)
	Calculates the Tversky Similarity [GSIM] of the bitsets bs1 and bs2. More...

Properties
	objectID = property(getObjectID)

Detailed Description

Functor class for calculating the Tversky Similarity [GSIM] of bitsets.

Constructor & Destructor Documentation

__init__() [1/2]

None CDPL.Descr.TverskySimilarity.__init__	(	float	alpha = 0.95,
		float	beta = 0.05
	)

Constructor.

Parameters

alpha	Weights the contribution of the first bitset.
beta	Weights the contribution of the second bitset.

__init__() [2/2]

None CDPL.Descr.TverskySimilarity.__init__

(

TverskySimilarity

func

)

Initializes a copy of the TverskySimilarity instance func.

Parameters

func	The TverskySimilarity instance to copy.

Member Function Documentation

getObjectID()

int CDPL.Descr.TverskySimilarity.getObjectID

(

)

Returns the numeric identifier (ID) of the wrapped C++ class instance.

Different Python TverskySimilarity instances may reference the same underlying C++ class instance. The commonly used Python expression a is not b thus cannot tell reliably whether the two TverskySimilarity instances a and b reference different C++ objects. The numeric identifier returned by this method allows to correctly implement such an identity test via the simple expression a.getObjectID() != b.getObjectID().

Returns

The numeric ID of the internally referenced C++ class instance.

assign()

TverskySimilarity CDPL.Descr.TverskySimilarity.assign

(

TverskySimilarity

func

)

Replaces the current state of self with a copy of the state of the TverskySimilarity instance func.

Parameters

func	The TverskySimilarity instance to copy.

Returns

self

__call__()

float CDPL.Descr.TverskySimilarity.__call__	(	Util.BitSet	bs1,
		Util.BitSet	bs2
	)

Calculates the Tversky Similarity [GSIM] of the bitsets bs1 and bs2.

The Tversky Similarity \( S_{ab} \) is calculated by:

[ S_{ab} = \frac{N_{ab}}{\alpha * N_a + \beta * N_b + N_{ab}} ]

where \( N_{ab} \) is the number of bits that are set in both bitsets, \( N_a \) is the number of bits that are only set in the first bitset and \( N_b \) is the number of bits that are only set in the second bitset. \( \alpha \) and \( \beta \) are bitset contribution weighting factors.

The Tversky measure is asymmetric. Setting the parameters \( \alpha = \beta = 1.0 \) makes it identical to the Tanimoto measure.

If the specified bitsets bs1 and bs2 are of different size, missing bits at the end of the smaller bitset are assumed to be zero.

Parameters

bs1	The first bitset.
bs2	The second bitset.

Returns

The calculated similarity measure.

See also

TverskySimilarity.TverskySimilarity()