ML-oxford

linear

$\hat{y} = \mathrm{X} \theta$

$X = \begin{bmatrix} x_{11}\end{bmatrix}$

$J(\theta) = (y - X\theta)^T (y - X\theta) = \sum_{i=1}^{n}(y_i - x_i^T\theta)^2$

matrix differentiation.