My doubt is about how could I represent this function: randperm (N, M) from MATLAB/GNU Octave or np.random.permutation from Python in a mathematical notation? I know that $N$, $M$ are about $n$ cols and $m$ rows respectively and I saw in wikipedia that authors represented matrix permutation https://en.wikipedia.org/wiki/Permutation_matrix as ${P_{\pi}}_{m,n}$ and I saw in a post here in Stack Exchange Mathematics channel that random variables could be represented as $R_{m,n}$ or $\mathbb{N} \hspace{0.2cm} \cap \hspace{0.2cm} [start, end]: start \in \mathbb{N}, end \in \mathbb{N}$ and $end > start$.
For example how could I describe mathematically this code?
BS = B(randperm(size(b,1)),:);
The code above tends to attribute the shuffled content of $B_{5,2}$ matrix to $BS$ with the same dimension $BS_{5,2}$ where B and BS are matrices.
Example: Let $B_{5,2}$ a matrix where: $B = \begin{bmatrix} 1 & 10\\ 2 & 20 \\ 3 & 30 \\ 4 & 40 \\ 5 & 50 \end{bmatrix}$
So $BS$ will be $BS_{5,2}$ and his values are the shuffled rows from $B$: $BS = \begin{bmatrix} 5 & 50\\ 2 & 20 \\ 3 & 30 \\ 1 & 10 \\ 4 & 40 \end{bmatrix}$ for example
I use to represent length as $N_{M_{m,n}}$ and size of a matrix as $(M_{m,n})$.