org.grouplens.lenskit.transform.normalize

## Interface VectorNormalizer

• ### Method Summary

All Methods
Modifier and Type Method and Description
VectorTransformation makeTransformation(SparseVector reference)
Create a vector transformation that normalizes and denormalizes vectors with respect to the specified entity.
MutableSparseVector normalize(SparseVector reference, MutableSparseVector target)
Normalize a vector in-place with a reference vector.
• ### Method Detail

• #### normalize

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

VectorTransformation makeTransformation(SparseVector reference)
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.