Notation for the ith row and column of a matrix

Question

When noting the $i^{th}$ scalar of a vector $\mathbf{x}$ one usually does it as $x_i$, since it is a scalar

When doing this for matrices that are being denoted in bold, let's say $\mathbf{A}$, how should I write the $i^{th}$ row or $j^{th}$ column?

This question provides some insight as to how to distinguish from rows and columns but does not address any possible standards for doing it as $\mathbf{A}_{i*}$, $A_{i*}$ or maybe even $\mathbf{a}_{i*}$

Is there a preferable form?

Answer 1

The notation I've usually seen for the $j^{\text{th}}$ column of a matrix $\mathbf{A}$ is to call it a column vector $\mathbf{a}_j$, just attaching the number of the column to the lowercase version of the letter used to denote the matrix. I don't know that I've seen a similar notation for the rows of a matrix, but $\mathbf{a}_{i*}$ seems like it would be the most consistent.

Answer 2

Here is a notation based on already standard notation: $({\bf A}^{\intercal})_{i}$ and ${\bf A}_{j}$ for the $i$-th row and the $j$-th column, respectively, of the matrix ${\bf A}$.