module 3 of 7 · 45 min

Trees

Use recursive feature splits to model nonlinear interactions.

Explain Trees clearlyImplement a small Trees exampleEvaluate whether Trees improves a simpler baselineIdentify failure cases and operational constraints
learning statenot started
0% completesign in to track progress
mental model

start with the idea before the implementation.

A tree partitions the feature space into regions that share similar predictions.
core concepts

the mechanisms you need to reason about.

01

Splits and impurity

Splits and impurity is studied through intuition implementation evidence and trade-offs. The goal is to be able to explain the mechanism and verify it with a concrete test rather than only repeat a definition.

02

Depth and overfitting

Depth and overfitting is studied through intuition implementation evidence and trade-offs. The goal is to be able to explain the mechanism and verify it with a concrete test rather than only repeat a definition.

03

Feature interactions

Feature interactions is studied through intuition implementation evidence and trade-offs. The goal is to be able to explain the mechanism and verify it with a concrete test rather than only repeat a definition.

04

Pruning

Pruning is studied through intuition implementation evidence and trade-offs. The goal is to be able to explain the mechanism and verify it with a concrete test rather than only repeat a definition.

engineering lab

turn the lesson into evidence.

LAB 1

train shallow and deep trees

Build the smallest version first. Record the input, expected output, measured result and one failure you discovered.

LAB 2

visualize a tree

Build the smallest version first. Record the input, expected output, measured result and one failure you discovered.

LAB 3

measure overfitting

Build the smallest version first. Record the input, expected output, measured result and one failure you discovered.

knowledge checks

prove you can explain and decide.

2

identify high-variance behavior

ask cortex to test me →
3

compare with a linear baseline

ask cortex to test me →
failure modes

what usually goes wrong.

risk

unbounded depth

Detect this early by defining a baseline, a measurable signal and a condition that would cause you to stop or redesign the approach.

risk

unstable feature importance

Detect this early by defining a baseline, a measurable signal and a condition that would cause you to stop or redesign the approach.

risk

assuming interpretability at scale

Detect this early by defining a baseline, a measurable signal and a condition that would cause you to stop or redesign the approach.

proof of learning

Create a short Trees engineering note with one working artifact one metric one failure case and one decision about when you would or would not use it.

Save the result in your portfolio or project repository. A strong learning artifact should make your assumptions, metrics and failure analysis visible.