The `AsFactor`

preprocessor is used to turn the integer values of the columns into sparse vectors where the value is 1
at the index that corresponds to the ‘category’ of that column. This is also known as “One Hot Encoding” in many other
packages.

`AsFactor`

takes no parameters.

```
import org.apache.mahout.math.algorithms.preprocessing.AsFactor
val A = drmParallelize(dense(
(3, 2, 1, 2),
(0, 0, 0, 0),
(1, 1, 1, 1)), numPartitions = 2)
// 0 -> 2, 3 -> 5, 6 -> 9
val factorizer: AsFactorModel = new AsFactor().fit(A)
val factoredA = factorizer.transform(A)
```