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Machine learning, from a straight line to neural networks

Fourteen interactive pages that build on each other. Start with what it means for a machine to learn from data, fit your first model with gradient descent, learn to spot and fix overfitting, then work up through neural networks and the ways attackers target ML systems.

Foundations · 01–04 Core techniques · 05–10 Neural networks & security · 11–14

RESOURCES

A small neural network classifying an email Four input features at the top feed two hidden layers of five neurons each, connected by weighted lines. Two output neurons at the bottom give the probability that the email is spam (0.94) or not spam (0.06). links CAPS sender length input layer features hidden layer 1 learned patterns hidden layer 2 combined patterns 0.94 spam 0.06 not spam output probability
How a network reads an email. Each input is a feature of the message, and each line is a learned weight: thicker means stronger, cyan weights are positive and amber weights are negative. The hidden layers combine those signals until the output gives a probability. By page 11 you will build one of these yourself.