Phase 2: Ensembles & Evaluation · ~90 minutes · Python

Feature Engineering & Selection

A good feature is worth a thousand data points.

Hiring signal: Understanding of feature engineering & selection internals

What you will learn

Implement numerical transforms (standardization, min-max scaling, log transform, binning) and explain when each is appropriate
Build one-hot, label, and target encoding for categorical features and identify the data leakage risk in target encoding
Construct a TF-IDF vectorizer from scratch and explain why it outperforms raw word counts for text classification
Apply filter-based feature selection (variance threshold, correlation, mutual information) to reduce dimensionality

Introduction

Type: Build Languages: Python Prerequisites: Phase 1 (Statistics for ML, Linear Algebra), Phase 2 Lessons 1-7 Time: ~90 minutes

Learning Objectives

Implement numerical transforms (standardization, min-max scaling, log transform, binning) and explain when each is appropriate
Build one-hot, label, and target encoding for categorical features and identify the data leakage risk in target encoding
Construct a TF-IDF vectorizer from scratch and explain why it outperforms raw word counts for text classification
Apply filter-based feature selection (variance threshold, correlation, mutual information) to reduce dimensionality

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