Math & Science ⇒ Matrix numbering

[bazman]

Hi there,

Last question for this evening:

I would like the matrix in the following to be given a number consistent with the other numebrs I am giving to my equations.

Code: Select all

\documentclass{article} % Your input file must contain these two lines
\usepackage{natbib}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{bm}
\usepackage{grffile}
\usepackage{graphicx}
\usepackage[%
  font=small,
  labelfont=bf,
  figurewithin=section,
  tablewithin=section,
  tableposition=top
]{caption}
\numberwithin{equation}{section}
\begin{document} % plus the \end{document} command at the end
\parskip = 1pc %change spacing between paragraphs
\parindent = 0pc %change paragraph indentation

\begin{equation}
\[ \left[ \begin{array}{lllll}
1 & a_1 & a_1a_2 & a_1a_2a_3 & a_1a_2a_3a_4 \\
a_1 & 1 & a_2 & a_2a_3 & a_2a_3a_4  \\
a_1a_2 & a_2 & 1 & a_3 & a_3a_4 \\
a_1a_2a_3 & a_2a_3 & a_3 & 1 & a_4 \\
a_1a_2a_3a_4 & a_2a_3a_4 & a_3a_4 & a_4 & 1 \end{array} \right]\]
\end{equation} 

\end{document}

[localghost]

Why do you use this construction?

Code: Select all

\begin{equation}
  \[
    % your math expression
  \]
\end{equation}

You should get several errors.


Best regards
Thorsten

[gmedina]

Hi,

instead of the array environment, you can use the bmatrix or pmatrix environments:

Code: Select all

\begin{equation}
  \begin{bmatrix}
    1 & a_1 & a_1a_2 & a_1a_2a_3 & a_1a_2a_3a_4 \\
    a_1 & 1 & a_2 & a_2a_3 & a_2a_3a_4  \\
    a_1a_2 & a_2 & 1 & a_3 & a_3a_4 \\
    a_1a_2a_3 & a_2a_3 & a_3 & 1 & a_4 \\
    a_1a_2a_3a_4 & a_2a_3a_4 & a_3a_4 & a_4 & 1 
  \end{bmatrix}
\end{equation}

[bazman]

ah that's great!

Is it possible to make it left justified?

[gmedina]

Of course:

Code: Select all

\begin{flalign}
  \begin{bmatrix}
    1 & a_1 & a_1a_2 & a_1a_2a_3 & a_1a_2a_3a_4 \\
    a_1 & 1 & a_2 & a_2a_3 & a_2a_3a_4  \\
    a_1a_2 & a_2 & 1 & a_3 & a_3a_4 \\
    a_1a_2a_3 & a_2a_3 & a_3 & 1 & a_4 \\
    a_1a_2a_3a_4 & a_2a_3a_4 & a_3a_4 & a_4 & 1
  \end{bmatrix} &&
\end{flalign}

[bazman]

sorry I did not mean that the matrix should be left aligned but rather the elements inthe matrix

[gmedina]

That's also possible. Two alternatives:

1) Using the array environment:

Code: Select all

\begin{equation}
  \left[% 
  \begin{array}{lllll}
    1 & a_1 & a_1a_2 & a_1a_2a_3 & a_1a_2a_3a_4 \\
    a_1 & 1 & a_2 & a_2a_3 & a_2a_3a_4  \\
    a_1a_2 & a_2 & 1 & a_3 & a_3a_4 \\
    a_1a_2a_3 & a_2a_3 & a_3 & 1 & a_4 \\
    a_1a_2a_3a_4 & a_2a_3a_4 & a_3a_4 & a_4 & 1 
  \end{array} 
  \right]
\end{equation} 

2) Using the bmatrix environment:

Code: Select all

\documentclass{article}
\usepackage{amsmath}

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

\begin{document}

\begin{equation}
  \begin{bmatrix}
    1 & a_1 & a_1a_2 & a_1a_2a_3 & a_1a_2a_3a_4 \\
    a_1 & 1 & a_2 & a_2a_3 & a_2a_3a_4  \\
    a_1a_2 & a_2 & 1 & a_3 & a_3a_4 \\
    a_1a_2a_3 & a_2a_3 & a_3 & 1 & a_4 \\
    a_1a_2a_3a_4 & a_2a_3a_4 & a_3a_4 & a_4 & 1
  \end{bmatrix}
\end{equation}

\end{document}

[bazman]

Prefect thank you!

[Stefan Kottwitz]

Hi bazman,

I did not mean that the matrix should be left aligned but rather the elements in the matrix

The solution of gmedina will effect all matrix environments like pmatrix, vmatrix, bmatrix etc. If you want to see a solution for matrices behaving like default but being more flexible have a look at an extension to amsmath matrix environments.

Stefan