longtable-to-xtab

title	author
Longtable-to-xtab - switch LaTeX table outputs from longtable to xtab	Julien Dutant

Longtable-to-xtab

Convert Pandoc's LaTeX table output from longtable to xtab.

v1.0. Copyright: © 2021 Julien Dutant [email protected] License: MIT - see LICENSE file for details.

Introduction

By default Pandoc outputs uses the LaTeX package longtable to format tables in LaTeX. However longtable environments cannot be used in a two column document or in a multiple columns environements (multicol). In those contexts one should use the supertabular or xtab packages - preferably xtab, which is based on supertabular and improves it.

This filter converts the LaTeX output of Pandoc for tables from longtable to xtab codes. It does so by implementing a suggestion of Bustel: redefine the longtable environment in LaTeX itself.

Usage

Installation

Copy longtable-to-xtab.lua in your document folder or in your pandoc data dir path.

Usage

Add -L longtable-to-xtab.lua to your Pandoc command line, or add filter: longtable-to-xtab.lua to a document's metadata block.

Details

Dependencies

Unlike longtable, the xtab and supertabular LaTeX packages are not included in the core list of LaTeX packages. In Linux Debian distributions they are included in the package texlive-latex-extra.

The duplicate headers issue and how the filter solves it

If a table has both headers and a caption, Pandoc generates a first header (caption and headers) and main header (headers only). See the code below for an illustration. If we simply turned the table into an xtabular and erase the \endfirsthead and \endhead commands we would get two header rows.

\begin{longtable}[]{@{}
  >{\centering\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.17}}
  >{\raggedright\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.11}}
  >{\raggedleft\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.22}}
  >{\raggedright\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.36}}@{}}
\caption{Here's the \emph{caption}. It, too, may span multiple
lines.}\tabularnewline
\toprule
Centered Header & Default Aligned & Right Aligned & Left
Aligned\footnote{Footnote in a table.} \\ \addlinespace
\midrule
\endfirsthead
\toprule
Centered Header & Default Aligned & Right Aligned & Left
Aligned{} \\ \addlinespace
\midrule
\endhead
First & row & 12.0 & Example of a row that spans multiple
lines. \\ \addlinespace
Second & row & 5.0 & Here's another one. Note the blank line between
rows. \\ \addlinespace
\bottomrule
\end{longtable}

Possible solutions:

1. Use \iffalse ...\endif to turn off LaTeX on the main header. This is the solution adopted here. It's a bit of a hack.

Limitation: from xtab's point of view the remaining first header row is a normal row. Not ideal if the table does span several pages.

2. strip the markdown table of its headers, and add the headers as \tablefirstheader (includes footnote) and \tableheader (footnotes stripped and other unique identifiers need to be stripped from the repeat header). See below Pandoc code without headers (the \toprule should be redefined to nothing).

\begin{longtable}[]{@{}
  >{\centering\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.17}}
  >{\raggedright\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.11}}
  >{\raggedleft\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.22}}
  >{\raggedright\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.36}}@{}}
\toprule
\endhead
First & row & 12.0 & Example of a row that spans multiple
lines. \\ \addlinespace
Second & row & 5.0 & Here's another one. Note the blank line between
rows. \\ \addlinespace
\bottomrule

and see below the ideal xtab code for the first and main headers:

\tablecaption{Here's the \emph{caption}. It, too, may span multiple
lines.}
\tablefirsthead{\toprule
Centered Header & Default Aligned & Right Aligned & Left
Aligned\footnote{Footnote in a table.} \\ \midrule}
\tablehead{\toprule Centered Header & Default Aligned & Right Aligned & Left Aligned \\ \midrule}
\begin{center}
\begin{xtabular}[]{@{}
  >{\centering\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.17}}
  >{\raggedright\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.11}}
  >{\raggedleft\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.22}}
  >{\raggedright\arraybackslash}p{(\columnwidth - 6\tabcolsep) * \real{0.36}}@{}}
First & row & 12.0 & Example of a row that spans multiple
lines. \\ \addlinespace
Second & row & 5.0 & Here's another one. Note the blank line between
rows. \\ \addlinespace
\bottomrule
\end{xtabular}
\end{center}

Contributing

PRs welcome.