How to put a full stop at the bottom, not mid-line, after an aligned matrix?

Question

How can I put a full stop at the bottom rather than at mid-line following the end of an aligned matrix expression such as $\begin{pmatrix} x\\ y \end{pmatrix}$?

Answer 1

You can place a stop with a second matrix (sans brackets) and phantom elements. The result is that the full stop is aligned as if next to bottom element in the matrix.

\documentclass{standalone}
\usepackage{amsmath}
\begin{document}
\begin{equation*}
\begin{pmatrix} x\\ y \end{pmatrix}\begin{matrix} \vphantom{x}\\ \vphantom{y}.\end{matrix}
\end{equation*}
\end{document}

The stop may look misaligned, but see the image below. The downside is that you have to include this phantom matrix, but it does work.

Answer 2

Something like \raisebox{\depth}{$\displaystyle\begin{pmatrix} x\\ y \end{pmatrix}$}. works. However, this is probably not a good idea from the typographic point of view: imagine the equation A=\begin{pmatrix} x\\ y \end{pmatrix}. Where would you put the full stop? I think the current default where matrix has nonzero depth (i.e. extends below the baseline) is right.

Here is the example:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\pagestyle{empty}
  \raisebox{\depth}{$\displaystyle\begin{pmatrix} x\\ y \end{pmatrix}$}.
\end{document}