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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:

${{R}_{1}}\left( {{x}_{pi}},{{G}_{q}},{{x}_{qj}} \right)=\,\left\{ \begin{matrix}
   +\infty  & p=q  \\
   \underset{l=1}{\overset{d}{\mathop \sum }}\,({{x}_{pi}}\left[ l \right]-{{x}_{qj}}\left[ l \right])\left( 2\left( {{x}_{qj}}\left[ l \right]-{{{\bar{x}}}_{q}}\left[ l \right] \right)+({{x}_{pi}}\left[ l \right]-{{x}_{qj}}\left[ l \right])(\left| {{G}_{q}} \right|-1)/|{{G}_{q}}| \right) & p\ne q  \\
\end{matrix} \right.$
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1  
Another way would be to replace +\infty with +\infty\hfill. This will move the +\infty to the left as desired. –  Peter Grill Sep 17 '12 at 5:56
    
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2 Answers 2

up vote 4 down vote accepted

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}

enter image description here

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

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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:

enter image description here

\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.

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

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