Consider a matrix $A\in\mathbb{R}^{n\times m}$ and another matrix, termed the index matrix, $B\in\{0,1\}^{n\times m}$.
What is the appropriate notation for a submatrix of $A$, call it $C$, built from the elements of $B$ that are one. Is $C=A(B)$ accepted?
Is there a better (more accepted) way to write this?