## Matrices with alignment

The entries of matrix columns are centered by default. Let’s see an example:

$\begin{pmatrix} 1 & 2 & 1 \\ 0 & -2 & -3 \\ 0 & 3 & -2 \end{pmatrix}$

Output:

For right alignment you could use an array environment instead of pmatrix. I will show a possibility to get left, right or centered alignment by redefining the internal amsmath macro \env@matrix. Its original definition in version 2.13 is:

\def\env@matrix{\hskip -\arraycolsep \let\@ifnextchar\new@ifnextchar \array{*\c@MaxMatrixCols c}}

I introduce an optional parameter, its default value is c:

\makeatletter \renewcommand*\env@matrix[1][c]{\hskip -\arraycolsep \let\@ifnextchar\new@ifnextchar \array{*\c@MaxMatrixCols #1}} \makeatother

Now, if you write \begin{pmatrix}[r] … above you will get:

This topic was discussed in the Matheplanet Forum.

05. May 2008 by stefan
Categories: Uncategorized | 2 comments

### Comments (2)

1. Thanks for this — I wish that it were in amslatex already!

2. You can also use the pmatrix* environment provided by the mathtools package like this:
begin{pmatrix*}[r]…