Maths for ML / Notation

\mathbf{X},\ A

capital letter (matrix)

Linear algebraBeginner

Say it “matrix X”

Capital letters usually mean a matrix. In ML, X is often the whole dataset: one row per example.

Example

\mathbf{X} \in \mathbb{R}^{n\times d}

n examples, d features each.

In code

X.shape == (n, d)

Where you’ll see it in ML

Design matrix X, weights W, attention matrices Q, K, V.

Don’t confuse it with

$\mathbf{x}$ bold lowercase (vector) Convention: bold lowercase is a vector, bold/capital is a matrix, plain italic is a scalar.

Lessons that use it

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