How can I use multicolumn or multirow in a tabular using the array package global formatting technique?

Question

Awhile ago, @robintw asked a practical question: Make first row of table all bold

It uses the array package to cleverly inject formatting code into the header row columns.

Clever Table Row Formatting Solution

\usepackage{array}
\newcolumntype{$}{>{\global\let\currentrowstyle\relax}} % Always set currentrowstyle to \relax in case no \rowstyle is used
\newcolumntype{^}{>{\currentrowstyle}} % set \currentrowstyle to \bfseries or whatever (>{\bfseries}c)
\newcommand{\rowstyle}[1]{\gdef\currentrowstyle{#1}% set global definition for \currentrowstyle
  #1\ignorespaces
}

The Problematic Code

I'd like to see multicolumn and multirow support. I tried the following based on https://tex.stackexchange.com/a/4816/13552, which does not work.

\documentclass{article}
\usepackage{array}
\newcolumntype{$}{>{\global\let\currentrowstyle\relax}}
\newcolumntype{^}{>{\currentrowstyle}}
\newcommand{\rowstyle}[1]{\gdef\currentrowstyle{#1}%
  #1\ignorespaces
}

\begin{document}
\begin{tabular}{$l^c^c^r}
\rowstyle{\bfseries}
%\multicolumn{2}{^l}{span2} & \multicolumn{2}{^r}{span2} \\ % Uncomment this to see problem
col1 & col2 & col3 & col4 \\
dat1 & dat2 & dat3 & dat4 \\
\end{tabular}
\end{document}

Your example works for me (TeXLive 2014, pdflatex), and produces the desired result. What error do you get? — anderstood, Jun 09 '15 at 15:41
@anderstood, uncommenting the problematic lines results in: ! Misplaced \omit. \multispan ->\omit \@multispan with This is XeTeX, Version 3.14159265-2.6-0.99991 (TeX Live 2014) (preloaded format=xelatex) — Jonathan Komar, Jun 11 '15 at 12:11

score 3 · Accepted Answer · edited Mar 05 '17 at 20:34

The problem has to do with the fact that the $> columntype is never used in the first row of the tabular at all.

You can address this by using:

\multicolumn{2}{$l}{}

For the first set of spanned columns. However, the problem then is that things get done in the wrong order. \rowstyle{\bfseries} is now before the start of the first cell. To address this, you can include it in the specification of the first cell

\multicolumn{2}{$l}{\rowstyle{\bfseries}span2}

which produces

spanned row styles

which, if I've understood correctly, is the expected result.

Complete code

\documentclass{article}
\usepackage{array}
\newcolumntype{$}{>{\global\let\currentrowstyle\relax}}
\newcolumntype{^}{>{\currentrowstyle}}
\newcommand{\rowstyle}[1]{\gdef\currentrowstyle{#1}%
  #1\ignorespaces
}

\begin{document}
  \begin{tabular}{$l^c^c^r}
    \multicolumn{2}{$l}{\rowstyle{\bfseries}span2} & \multicolumn{2}{^r}{span2} \\ % Uncomment this to see problem
    col1 & col2 & col3 & col4 \\
    dat1 & dat2 & dat3 & dat4 \\
  \end{tabular}
\end{document}

Thanks! Finally an answer to this. Not a clean solution (because the $ and ^ have to be mentioned again :/), but it will suffice for now! Thanks for providing a nice explanation. It is always helpful to understand things. — Jonathan Komar, Jun 12 '15 at 06:19
@macmadness86 I agree it is not a perfect solution. However, since this question had been unanswered for a while, I thought even an imperfect one preferable to none at all. Maybe somebody else will suggest a nice trick to improve things further (I just followed my nose). Hopefully latex3 will eventually offer more significant improvements! — cfr, Jun 12 '15 at 12:31

How can I use multicolumn or multirow in a tabular using the array package global formatting technique?

Clever Table Row Formatting Solution

The Problematic Code

1 Answers1

Complete code