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Representation learning

As explained in Outlier Detection in Python

Representation learning is the process of learning useful numerical representations of objects from data.

Representation learning finds useful numerical representations of objects from data. In deep learning, these representations are often embeddings: values from a trained network's second-last layer, selected because they preserve information useful for prediction. section 16.5.1

A practical workflow is:

  • Train a neural network on a prediction or self-supervised pretext task. section 16.5.1
  • Extract embeddings from the second-last layer rather than using the final prediction. section 16.5.1
  • Use the embeddings as input to classifiers, regressors, or other predictive models. section 16.5.1

Learning from image transformations

A network can learn to predict whether an image was cropped, discolored, stretched, or rotated. Its second-last-layer values then represent image characteristics for later prediction tasks. section 16.5.1

How Outlier Detection in Python covers it

How deep it goes
Explains embedding extraction and reuse, while stopping short of detailed network architecture or training mathematics.
Examples
Uses transformed images, image rotations, and tabulated mug-image embeddings as concrete examples.
What you can do after
Apply learned embeddings as inputs to downstream predictive models with less labeled data.
How it connects
Links embeddings with self-supervised learning, neural networks, classifiers, regressors, XGBoost, and CatBoost.

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This explainer was generated by Manning's knowledge graph from the text of Outlier Detection in Python. The section links point to the parts of the book it draws on.