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Feature interaction

As explained in Outlier Detection in Python

A feature interaction is a dependency in which the effect of one feature on a model output varies according to the value of another feature.

A feature interaction occurs when one feature’s relationship with an outlier score changes according to another feature’s value. A global importance ranking can hide this dependency. section 13.2.1

Height and length in abalone data

Height may relate differently to an outlier score at different lengths. Replacing the original variables with an interpretable ratio such as height divided by length can expose the dependency; proxy models offer another route. section 13.2.1

Feature importance estimates provide useful context but do not readily reveal interactions. SHAP is preferred where possible, while approximate alternatives may misorder or equalize feature contributions. section 13.2.1

How Outlier Detection in Python covers it

How deep it goes
Defines the dependency and gives engineered-feature and proxy-model remedies, but does not develop interaction-detection procedures.
Examples
Uses abalone height and length, a height-to-length ratio, SHAP explanations, and PyOD importance rankings.
What it assumes
Assumes familiarity with outlier scores and feature importances; does not teach interaction detection from first principles.
What you can do after
Evaluate outlier explanations by testing engineered features or comparing SHAP with approximate importance estimates.
How it connects
Connects feature engineering, feature importance, SHAP, proxy models, and outlier detection.

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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.