19

How to add a matrix in LaTeX?

23

Ash's answer typesets the matrix inline with the text. A (perhaps) nicer way to do this is to use the smallmatrix environment in the amsmath package. Add to the document preamble:

\usepackage{amsmath}

And then you can do:

$M = \begin{smallmatrix} a&b\\ c&d \end{smallmatrix}$

If you want to bracket the matrix you can also do:

$M = \left( \begin{smallmatrix} a&b\\ c&d \end{smallmatrix} \right)$

The amsmath package also offers the shortcut matrix environments which default to centered alignment for their columns:

  • matrix: unbracketed matrix
  • pmatrix: matrix surrounded by parentheses
  • bmatrix: matrix surrounded by square brackets
  • vmatrix: matrix surrounded by single vertical lines
  • Vmatrix: matrix surrounded by double vertical lines

This info found in "The LaTeX Companion".

16

First: if you intend to do math in LaTeX, you SHOULD learn and use AMS LaTeX. The best reference is the Short Math Guide for LaTeX. In this guide, you will learn that there are many different matrix macros available when you use the amsmath package (e.g., \usepackage{amsmath} ).

To quote the document,

4.4. Matrices The environments pmatrix, bmatrix, Bmatrix, vmatrix and Vmatrix have (respectively) ( ), [ ], { }, | |, and || || delimiters built in. There is also a matrix environment sans delimiters, and an array environment that can be used to obtain left alignment or other variations in the column specs. [ed. To produce a matrix with parenthesis around it, use:]

\begin{pmatrix} 
  \alpha     & \beta^{*}\\ 
  \gamma^{*} & \delta 
\end{pmatrix}

To produce a small matrix suitable for use in text, there is a smallmatrix environment [ed. here was a matrix appropriate for text mode] that comes closer to fitting within a single text line than a normal matrix. This example was produced by

\bigl( \begin{smallmatrix} 
  a & b\\
  c & d 
\end{smallmatrix} \bigr)

To produce a row of dots in a matrix spanning a given number of columns, use \hdotsfor. For example, \hdotsfor{3} in the second column of a four-column matrix will print a row of dots across the final three columns.

Note. The plain TeX form \matrix{...\cr...\cr} and the related commands \pmatrix, \cases should be avoided in LaTeX (and when the amsmath package is loaded they are disabled).

Finally, I'd like to mention that, while it is possible to set matrices without AMS LaTeX, just use it. It offers so many benefits that until you get the hang of LaTeX, it's the best single macro package for math.

7 accepted

For a matrix of the form:

M = x y
    z w

use the LaTeX code:

$M =
\begin{array}{cc}
x & y \\
z & w \\
\end{array}$
0

I agree with Ashwin's simple approach. Sometimes you can't rely on amsmath being available, so if you're after straightforward matrices, then use straightforward Latex commands. See more at http://andy-roberts.net/misc/latex/latextutorial9.html for how to wrap your 'array' in brackets.

0
$M = 
\left[ {\begin{array}{*{20}c}
   x & y  \\
   z & w  \\

 \end{array} } \right]
$

$M = 
\left( {\begin{array}{*{20}c}
   x & y  \\
   z & w  \\

 \end{array} } \right)
$

$M = 
\left| {\begin{array}{*{20}c}
   x & y  \\
   z & w  \\

 \end{array} } \right|
$
0

For flexible typesetting of matrices with color, lines and justifivation done by formatting parameters see An extension to amsmath matrix environments.