How to trim \toprule (from booktabs package)?
It is probably something basic I'm missing, but I need it and it's nowhere to be found.
1 Answer
If I understand your objective correctly, you want the lines generated by \toprule -- and by \midrule and \bottomrule too, right? -- start at the left-hand edge and end at the right-hand edge of the contents of the table.
To achieve this objective, you could specify @{} as the first and last items in the argument of a tabular, tabular*, tabularx, etc. environment:
\documentclass{article}
\usepackage{booktabs}
\begin{document}
\noindent
\begin{tabular}{ @{} lccr @{} } % @{} suppresses the whitespace in the corresponding position
\toprule
long story & about & absolutely & nothing \\
\midrule
aa & bb & cc & dd\\
\multicolumn{2}{@{}l}{First thoughts \dots }\\ % note the @{} item before "l"
& & \multicolumn{2}{r@{}}{\dots Final thoughts}\\ % note the @{} item after "r"
\bottomrule
\end{tabular}
\end{document}
The MWE also illustrates that if your table has \multicolumn directives that encompass the first or final columns of the table, you'll again need to supply @{} items, as appropriate, this time in the second argument of the \multicolumn command.
By the way, I believe that suppressing the whitespace at the far left and far right edges of a table is something that the author of the booktabs package recommends doing; see, e.g., the tabular environment at the top of page 5 of the package's user guide; the output of that code is shown on p. 2 of the guide.
\toprule[1mm]for example(lr)thing does to\cmidrule(lr).2\tabcolsep) that is usually inserted between columns is also inserted before and after the first and the last column (but only one\tabcolsep).)