Maths for ML / Notation

\det(\mathbf{A}),\ |\mathbf{A}|

determinant

Linear algebraIntermediate

Say it “determinant of A”

One number that says how much A scales area/volume. Zero means A squashes space flat and has no inverse.

Example

\det\begin{bmatrix}2&0\\0&3\end{bmatrix} = 6

In code

np.linalg.det(A)

torch.linalg.det(A)

Where you’ll see it in ML

Gaussian densities, normalizing flows (log-det of the Jacobian).

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.
$|x|$ absolute value Distance from zero, always non-negative. For a set, |S| is the number of elements.

Lessons that use it

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