$A = \begin{bmatrix}1 & 0 & 0\\0 & 1 & 0\\0 & 0 & 1\end{bmatrix}, B = \begin{bmatrix}2 & 3\end{bmatrix}, C = \begin{bmatrix}1 & 0 & 2\\0 & 1 & 3\\0 & 0 & 1\end{bmatrix}$
I have the identity matrix $A$, and the row vector $B$ which has a different length to $A$, what is the notation the get the result $C$? i.e. replacing the 3 column of $A$ with all the values of $B$ that will fit.