From entry non-linear transformations in glossary Artificial Intelligence: humans at the heart of algorithms
A non-linear transformation modifies features of dataset or a using a non-linear function, for example dividing subsequent elements of a time series (a1/a0, a2/a1, a3/a2, ...). These may be used instead of the original data or used in addition to it. By adding non-linear diversity to the original data, it may be possible to use simpler subsequent methods.
Also used in hcistats2e: Chap. 11: page 130