[Tex/LaTex] What does the \ra command do

Question

I'm trying to understand the following code. What does \ra do?

\begin{table*}\centering  
\ra{1.3}  
\begin{tabular}{@{}rrrrcrrrcrrr@{}}\toprule  
& \multicolumn{3}{c}{$w = 8$} & \phantom{abc}& \multicolumn{3}{c}{$w = 16$} &
\phantom{abc} & \multicolumn{3}{c}{$w = 32$}\\
\cmidrule{2-4} \cmidrule{6-8} \cmidrule{10-12}
& $t=0$ & $t=1$ & $t=2$ && $t=0$ & $t=1$ & $t=2$ && $t=0$ & $t=1$ & $t=2$\\ \midrule  
$dir=1$\\  
$c$ & 0.0790 & 0.1692 & 0.2945 && 0.3670 & 0.7187 & 3.1815 && -1.0032 & -1.7104 & -21.7969\\  
$c$ & -0.8651& 50.0476& 5.9384&& -9.0714& 297.0923& 46.2143&& 4.3590& 34.5809& 76.9167\\  
$c$ & 124.2756& -50.9612& -14.2721&& 128.2265& -630.5455& -381.0930&& -121.0518& -137.1210& -220.2500\\  
$dir=0$\\  
$c$ & 0.0357& 1.2473& 0.2119&& 0.3593& -0.2755& 2.1764&& -1.2998& -3.8202& -1.2784\\  
$c$ & -17.9048& -37.1111& 8.8591&& -30.7381& -9.5952& -3.0000&& -11.1631& -5.7108& -15.6728\\  
$c$ & 105.5518& 232.1160& -94.7351&& 100.2497& 141.2778& -259.7326&& 52.5745& 10.1098& -140.2130\\  
\bottomrule  
\end{tabular}  
\caption{Caption}  
\end{table*}  

Answer 1

Most likely you'll find

\newcommand{\ra}[1]{\renewcommand{\arraystretch}{#1}}

In your document, but I think you shouldn't use it. With \ra{1.3} the distance between rows will increase by 30%, which can be useful in certain situations, but here it will just spread out the data without any real benefit.

Rather, you should separate the two parts of the table with a small vertical space. Also the \phantom{abc} columns are just a waste of space. Using siunitx and S columns provides for consistent typesetting of numbers.

\documentclass{article}
\usepackage[margin=0.5cm]{geometry}
\usepackage{booktabs}
\usepackage{siunitx}

\begin{document}

\begin{table*}
\centering

\begin{tabular}{@{}r*{9}{S[table-format=-3.4]}@{}}
\toprule
& \multicolumn{3}{c}{$w = 8$} & \multicolumn{3}{c}{$w = 16$} & \multicolumn{3}{c}{$w = 32$}\\
\cmidrule(lr){2-4} \cmidrule(lr){5-7} \cmidrule(l){8-10}
& {$t=0$} & {$t=1$} & {$t=2$} & {$t=0$} & {$t=1$} & {$t=2$} & {$t=0$} & {$t=1$} & {$t=2$} \\
\midrule  
$dir=1$\\  
$c$ & 0.0790 & 0.1692 & 0.2945 & 0.3670 & 0.7187 & 3.1815 & -1.0032 & -1.7104 & -21.7969\\  
$c$ & -0.8651& 50.0476& 5.9384& -9.0714& 297.0923& 46.2143& 4.3590& 34.5809& 76.9167\\  
$c$ & 124.2756& -50.9612& -14.2721& 128.2265& -630.5455& -381.0930& -121.0518& -137.1210& -220.2500\\  
\addlinespace
$dir=0$\\  
$c$ & 0.0357& 1.2473& 0.2119& 0.3593& -0.2755& 2.1764& -1.2998& -3.8202& -1.2784\\  
$c$ & -17.9048& -37.1111& 8.8591& -30.7381& -9.5952& -3.0000& -11.1631& -5.7108& -15.6728\\  
$c$ & 105.5518& 232.1160& -94.7351& 100.2497& 141.2778& -259.7326& 52.5745& 10.1098& -140.2130\\  
\bottomrule  
\end{tabular}  
\caption{Caption}  
\end{table*}  

\end{document}