How to obtain a square matrix of the diagonal elements and 0 ？

[hunter1992]

For example, I got a square matrix named A:

$$A = \begin{bmatrix} a_{11}&a_{12}&a_{13}\\ a_{21}&a_{22}&a_{23}\\ a_{31}&a_{32}&a_{33}\\ \end{bmatrix}$$

Now I wanna get a matrix B from A by nalgebra:

$$B = \begin{bmatrix} a_{11}&0&0\\ 0&a_{22}&0\\ 0&0&a_{33}\\ \end{bmatrix}$$

I have checked the document, but didn't find any func works.

NEED HELP~