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# Preprocessing / feature extraction

mlpack provides a number of utilities for data preparation and feature
extraction.  These utilities are generally used just before actually applying
any machine learning [transformations](transformations.md) or
[modeling](modeling.md).

*Note: this section is under construction and not all functionality is
documented yet.*

 * [Normalizing labels](core/normalizing_labels.md): convert labels to/from an
   arbitrary range to `[0, numClasses - 1]`, which is the range that mlpack
   classifiers require.

 * [Dataset splitting](core/split.md): split a dataset into a training and test
   set, optionally including labels.

 * [Image preprocessing](core/images.md): functions to preprocess
   images for training and inference, including resizing, cropping, and changing
   the pixel ordering.

 * [Imputation](core/imputation.md): replace missing values in a dataset with
   imputed values using a variety of imputation strategies.
