Maths for ML / Notation

\mathbf{I}_n

identity matrix

Linear algebraBeginner

Say it “identity / I n”

Square matrix with 1s on the diagonal and 0s elsewhere. Multiplying by it changes nothing.

Example

\mathbf{I}\mathbf{x} = \mathbf{x}

In code

np.eye(n)

torch.eye(n)

Where you’ll see it in ML

Ridge regression adds λI; residual connections are 'identity plus a little'.

Don’t confuse it with

$\mathbf{A}^{-1}$ matrix inverse The matrix that undoes A: A⁻¹A = I. Only exists for square, non-singular matrices.

Lessons that use it

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