# How to justify an element in matrix

I have a formula in LaTeX attached below. But I could not justify the position of $+\infty$ symbol. I want it appear just after the $\{$ and aligns to the left of the second term.

The LaTeX Code:

${{R}_{1}}\left( {{x}_{pi}},{{G}_{q}},{{x}_{qj}} \right)=\,\left\{ \begin{matrix} +\infty & p=q \\ \underset{l=1}{\overset{d}{\mathop \sum }}\,({{x}_{pi}}\left[ l \right]-{{x}_{qj}}\left[ l \right])\left( 2\left( {{x}_{qj}}\left[ l \right]-{{{\bar{x}}}_{q}}\left[ l \right] \right)+({{x}_{pi}}\left[ l \right]-{{x}_{qj}}\left[ l \right])(\left| {{G}_{q}} \right|-1)/|{{G}_{q}}| \right) & p\ne q \\ \end{matrix} \right.$


## 2 Answers

I would use a cases environment (from the amsmath package):

\documentclass[10pt]{article}
\usepackage{amsmath}

\begin{document}

${{R}_{1}}( {{x}_{pi}},{{G}_{q}},{{x}_{qj}} ) = \begin{cases} +\infty & p=q \\ \sum\limits_{l=1}^{d}\,({{x}_{pi}}[ l ]-{{x}_{qj}} [ l ])\bigl( 2( {{x}_{qj}} [ l ]-{{{\bar{x}}}_{q}} [ l] \bigr)+({{x}_{pi}}[ l ]-{{x}_{qj}} [ l])(\lvert {{G}_{q}} \rvert|-1)/\lvert{{G}_{q}}\rvert ) & p\ne q \\ \end{cases}$

\end{document} I removed some superfluous \left, \right constructs and replaced one of them with \bigl, \bigr.

• The formula works correctly in Latex. However, I'm not sure if I can export it to other environments such as MathType or not. By the way, thank you for your help. – remo Sep 17 '12 at 5:19

You can use an array instead, and then indicate the column specification. For example, using @{}lc produces a similar layout to your matrix yet left-aligned: \documentclass{article}
\usepackage{amsmath}% http://ctan.org/pkg/amsmath
\begin{document}
${{R}_{1}}\left( {{x}_{pi}},{{G}_{q}},{{x}_{qj}} \right)=\,\left\{ \begin{matrix} +\infty & p=q \\ \underset{l=1}{\overset{d}{\mathop \sum }}\,({{x}_{pi}}\left[ l \right]-{{x}_{qj}}\left[ l \right])\left( 2\left( {{x}_{qj}}\left[ l \right]-{{{\bar{x}}}_{q}}\left[ l \right] \right)+({{x}_{pi}}\left[ l \right]-{{x}_{qj}}\left[ l \right])(\left| {{G}_{q}} \right|-1)/|{{G}_{q}}| \right) & p\ne q \\ \end{matrix} \right.$

${{R}_{1}}({{x}_{pi}},{{G}_{q}},{{x}_{qj}})=\left\{ \begin{array}{@{}lc} +\infty & p=q \\ \sum\limits_{l=1}^d\,({{x}_{pi}}[ l ]-{{x}_{qj}}[ l ])( 2( {{x}_{qj}}[ l ]-{{{\bar{x}}}_{q}}[ l ] )+({{x}_{pi}}[ l ]-{{x}_{qj}}[ l ])(| {{G}_{q}} |-1)/|{{G}_{q}}| ) & p\ne q \\ \end{array} \right.$

\end{document}


The excessive use of \left and \right is not required. It introduces unwanted spacing and doesn't add any value. Consider using less-invasive constructions like \bigl and \bigr.

• But When I paste your code in MathType, it does not change the display. – remo Sep 17 '12 at 5:08