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Feature scaling

As explained in Machine Learning System Design

Feature scaling is the transformation of numerical input features to comparable numerical ranges or scales.

Feature scaling transforms numerical inputs into comparable ranges or scales. It commonly appears as a preprocessing step before a model, alongside feature engineering such as one-hot encoding. section 10.1.1 section 11.1.2

Use scaling with attention to the model and the surrounding pipeline:

  • Include scaling consistently in the model pipeline so preprocessing forms part of the ordered path from input data to predictions. section 10.1.1
  • Treat scaling as one option among numeric transformations, alongside normalization and mathematical functions such as logarithms. section 11.1.2
  • Do not assume scaling improves every model: gradient boosting metrics may remain unchanged after monotonic transformations because decision trees are invariant to them. section 11.1.2

A simple classifier pipeline

A logistic regression classifier can be enhanced with a feature scaling step, producing a model pipeline that may also include one-hot encoding for categorical variables. section 10.1.1

How Machine Learning System Design covers it

How deep it goes
Identifies scaling as a numeric transformation and contrasts its model-dependent value without deriving procedures or formulas.
Examples
Uses a logistic regression pipeline and contrasts scaling with monotonic transformations applied to gradient boosting features.
What you can do after
Apply scaling as a numeric preprocessing step and judge whether it fits the chosen model.
How it connects
Connects scaling with preprocessing, feature engineering, normalization, logarithmic transformation, logistic regression, and gradient boosting.

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This explainer was generated by Manning's knowledge graph from the text of Machine Learning System Design. The section links point to the parts of the book it draws on.