Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

My top favorite of my answers (sorted with easiest to understand first): rank 2: Matrix Representation 3-D Imaging: simplifying equations Sub-Matrix: Efficient Inverse QR: Fundamental Subspaces Sylvester Equation: Explicit $2 \times 2$ Pseudo-inverse: Efficient and simple calculation Unitary Similarity: python code to "hollow a matrix" Furthest in angle vector: "Box Rotation" Also: norm as symmetric and skew symmetric