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Sign function

As explained in Machine Learning Algorithms in Depth

A sign function returns the sign of a numeric input, commonly mapping positive and negative values to +1 and −1.

The sign function converts a linear score into a binary label, mapping positive and negative values to +1 and −1. In a perceptron, h(x; θ) applies it to θ·x + θ₀. section 5.2

Linear decision boundary

The equation θ·x + θ₀ = 0 defines the decision boundary. Points on the normal-vector side receive +1; points on the opposite side receive −1. section 5.2

How Machine Learning Algorithms in Depth covers it

How deep it goes
Defines the binary mapping and connects it to a hyperplane, without developing the function beyond linear classification.
Examples
Uses a perceptron classifier on the iris dataset and illustrates its two-dimensional decision boundary.
What it assumes
Uses feature vectors, parameters, inner products, offsets, and binary labels in {+1, −1}.
What you can do after
Evaluate a linear score as a binary classification prediction.
How it connects
Connects sign function to perceptrons, linear classifiers, inner products, hyperplanes, decision boundaries, and binary labels.

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