What is the correct way of doing a minus sign in a LaTeX Table? The minus sign I'm doing seems much longer than the minus sign in math mode.

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Surround the entire number with . Example $-5$ that puts it in math mode. If that does not work, please provide a MWE that shows the problem. –  Peter Grill Feb 10 '12 at 21:24
no, it is the other way round: the minus in math mode is longer than the hyphen character –  Herbert Feb 10 '12 at 21:26
@Herbert: I suspect the OP is using --- and it is too long. –  Peter Grill Feb 10 '12 at 21:29
@PeterGrill: Maybe, but without an example we can only guess ... –  Herbert Feb 10 '12 at 21:33

A minus sign in a table should be typeset in math mode to get the proper size and spacing:

The amsmath package is only required for the line where \text is used.

\documentclass{article}
\usepackage{amsmath}% only needed for last case where \text{} is used
\begin{document}
\begin{tabular} { l c }
minus sign outside math mode (incorrect) & -5 \\
minus sign inside math mode  & $-5$\\
minus sign but not for a number  & $-$foo\\
minus sign but not for a number  & $-\text{foo}$
\end{tabular}
\end{document}

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What about \noindent\llap{-}5? –  J G Feb 10 '12 at 21:35
@JG: This would still have incorrect spacing between the operator and the operand. Moreover, if used with other surrounding text, the spacing would be wrong. –  Werner Feb 10 '12 at 21:38
Then what does that do? And, what is all of this foo stuff? I see lots of foo talk out there in latex land. –  J G Feb 10 '12 at 21:42
@JG: I just used foo to indicate random text. It not a specific command. –  Peter Grill Feb 10 '12 at 21:43
@JG: I think that you misunderstood what you read. You should post a separate question as the purpose of \llap is not to produce a minus sign. –  Peter Grill Feb 10 '12 at 21:52