org.lenskit.transform.normalize

Interface VectorNormalizer

All Known Implementing Classes:

AbstractVectorNormalizer, IdentityVectorNormalizer, MeanCenteringVectorNormalizer, MeanVarianceNormalizer, UnitVectorNormalizer

@DefaultImplementation(value=IdentityVectorNormalizer.class)
public interface VectorNormalizer

Normalize vectors by applying a reversible transformation with respect to a reference vector. The reference vector is used to compute the normalization, and it is applied to the target vector; this allows e.g. the user’s average rating to be subtracted from a set of ratings.

Method Summary

Modifier and Type	Method and Description
InvertibleFunction<Long2DoubleMap,Long2DoubleMap>	makeTransformation(Long2DoubleMap reference) Create a vector transformation that normalizes and denormalizes vectors with respect to a reference vector.
VectorTransformation	makeTransformation(SparseVector reference) Deprecated. Use makeTransformation(Long2DoubleMap).
MutableSparseVector	normalize(SparseVector reference, MutableSparseVector target) Deprecated. Old vectors are going away.

Method Detail

normalize

@Deprecated
MutableSparseVector normalize(@Nonnull
                                           SparseVector reference,
                                           @Nullable
                                           MutableSparseVector target)

Deprecated. Old vectors are going away.

Normalize a vector in-place with a reference vector.

To understand the relationship of reference and vector, consider wanting to subtract the user’s mean rating from a set of ratings. To do that, the user’s rating vector is reference, and the vector of ratings to be adjusted is vector.

This method is equivalent to makeTransformation(reference).apply(target).

Parameters:

reference - The reference used to compute whatever transformation is needed (e.g. the mean value).

target - The vector to normalize. If null, a new mutable copy of reference is created.

Returns:

target, or a normalized mutable copy of reference if target is null.

makeTransformation

@Deprecated
VectorTransformation makeTransformation(SparseVector reference)

Deprecated. Use makeTransformation(Long2DoubleMap).

Create a vector transformation that normalizes and denormalizes vectors with respect to the specified entity. This allows transformations to be applied multiple times to different vectors and also unapplied.

If the reference vector is empty, the returned transformation should be the identity transform. Results are undefined if the reference vector is not complete or contains NaN values.

If the normalization needs to retain a copy of the sparse vector, it will take an immutable copy.

Parameters:

reference - The reference vector.

Returns:

A transformation built from the reference vector.

makeTransformation

InvertibleFunction<Long2DoubleMap,Long2DoubleMap> makeTransformation(Long2DoubleMap reference)

Create a vector transformation that normalizes and denormalizes vectors with respect to a reference vector. The reference vector is used to compute any data needed for the normalization. For example, a mean-centering normalization will subtract the mean of the reference vector from any vector to which it is applied, and add back the reference mean when it is unapplied.

This allows transformations to be applied multiple times to different vectors and also unapplied.

If the reference vector is empty, the returned transformation should be the identity transform. Results are undefined if the reference vector is not complete or contains NaN values.

If the normalization needs to retain a copy of the sparse vector, it will take an immutable copy.

Parameters:

reference - The reference vector.

Returns:

A transformation built from the reference vector.