Vrftsjtryk

I would like to find a way to better align signed fractions in a table. Take the following example:

documentclass{article}

usepackage{amsmath}

usepackage{booktabs}



begin{document}



begin{table}

  centering

  begin{tabular}{rr} toprule

    $alpha$ & $beta$ \ midrule

    $-frac{9}{2}$ & $-frac{1}{6}$ \[0.8ex] 

    $-frac{7}{2}$ & $frac{1}{30}$ \[0.5ex]                                  

    bottomrule

  end{tabular}

end{table}



end{document}

This gives:

I don't like the look of the second column, which I think would look better if 1/30 would be centrally aligned with 1/6. By playing around, I noticed that changing the type of the second column to c and adding a phantom{-} in front of 1/30, i.e.,

begin{table}

  centering

  begin{tabular}{rc} toprule

    $alpha$ & $beta$ \ midrule

    $-frac{9}{2}$ & $-frac{1}{6}$ \[0.8ex] 

    $-frac{7}{2}$ & $phantom{-}frac{1}{30}$ \[0.8ex]                                  

    bottomrule

  end{tabular}

end{table}

I get what I think is a much better looking result:

This, however, requires that I manually add the phantom{-} command for every positive entry in my tables: I want to avoid this because the tables are large. So I have two questions:

1. Is there a way in LaTeX or through a package which I can automate the addition of phantom{-}?


2. Do you know of a better way to get the kind of alignment of fractions I'm looking for?

I don't think there's anything wrong with standard center alignment. Consider the case where you have -1/6 and -1/30: if you center align the fractions, the minus signs will be off.

I can offer a new column type for the columns with negative entries.

documentclass{article}

usepackage{amsmath,mathtools}

usepackage{booktabs,array,calc}



newcolumntype{n}{@{hspace{dimexprfontcharwdtextfont2 0+arraycolsep}}c}

newcommand{?}{mathllap{-}}

newcommand{mcn}[1]{%

  multicolumn{1}{c}{kern-fontcharwdtextfont2 0 #1}%

}



begin{document}



begin{table}

centering



$begin{array}{nnc}

toprule

mcn{alpha} & mcn{beta} & gamma \

midrule

?frac{9}{2} & ?frac{1}{6}  & 2 \[0.8ex]

?frac{7}{2} &   frac{1}{30} & 3 \[0.5ex]

bottomrule

end{array}$



end{table}



end{document}