| Interface | Description | 
|---|---|
| VectorTransformer | Trait for transformation of a vector | 
| Class | Description | 
|---|---|
| ChiSqSelector | Creates a ChiSquared feature selector. | 
| ChiSqSelectorModel | Chi Squared selector model. | 
| ChiSqSelectorModel.SaveLoadV1_0$ | |
| ElementwiseProduct | Outputs the Hadamard product (i.e., the element-wise product) of each input vector with a
 provided "weight" vector. | 
| HashingTF | Maps a sequence of terms to their term frequencies using the hashing trick. | 
| IDF | Inverse document frequency (IDF). | 
| IDF.DocumentFrequencyAggregator | Document frequency aggregator. | 
| IDFModel | Represents an IDF model that can transform term frequency vectors. | 
| Normalizer | Normalizes samples individually to unit L^p^ norm | 
| PCA | A feature transformer that projects vectors to a low-dimensional space using PCA. | 
| PCAModel | Model fitted by  PCAthat can project vectors to a low-dimensional space using PCA. | 
| PCAUtil | |
| StandardScaler | Standardizes features by removing the mean and scaling to unit std using column summary
 statistics on the samples in the training set. | 
| StandardScalerModel | Represents a StandardScaler model that can transform vectors. | 
| VocabWord | Entry in vocabulary | 
| Word2Vec | Word2Vec creates vector representation of words in a text corpus. | 
| Word2VecModel | Word2Vec model
 param:  wordIndex maps each word to an index, which can retrieve the corresponding
                  vector from wordVectors
 param:  wordVectors array of length numWords * vectorSize, vector corresponding
                    to the word mapped with index i can be retrieved by the slice
                    (i * vectorSize, i * vectorSize + vectorSize) |