How do I create the headings for this multirow multicolum table?

Question

I wish to create a table that looks like the following:

+-------++--------------------------++--------------------------+
|       ||          Category A      ||         Category B       |
| Title ++--------+--------+--------++--------+--------+--------+
|       || Item 1 | Item 2 | Item 3 || Item 1 | Item 2 | Item 3 |
+-------++--------+--------+--------++--------+--------+--------+
|   X   || 1      | 2      | 3      || 1      | 2      | 3      |
+-------++--------+--------+--------++--------+--------+--------+
|   Y   || 1      | 2      | 3      || 1      | 2      | 3      |
+-------++--------+--------+--------++--------+--------+--------+

but I am having great difficulty in formatting it like this.

What latex code structures the headings like that shown above?

I have looked at the reference page here: http://en.wikibooks.org/wiki/LaTeX/Tables but despite my experimentations I was unable to obtain this effect.

Answer 1

Here is a duplicate of what you're after:

\documentclass{article}
\usepackage{multirow}% http://ctan.org/pkg/multirow
\begin{document}
\begin{tabular}{|c||l|l|l||l|l|l|}
  \hline
  \multirow{2}{*}{Title} 
      & \multicolumn{3}{c||}{Category~A} 
          & \multicolumn{3}{|c|}{Category~B} \\             \cline{2-7}
  & Item~1 & Item~2 & Item~3 & Item~1 & Item~2 & Item~3 \\  \hline
  $X$ & 1 & 2 & 3 & 1 & 2 & 3 \\      \hline
  $Y$ & 1 & 2 & 3 & 1 & 2 & 3 \\      \hline
\end{tabular}
\end{document}

Here is a consideration:

The booktabs package provides a really beautiful typesetting environment for tables, but enforces some strict rules to obtain them. One of these is to never, ever use vertical lines. The reason for this is that the columnar alignment of all the entries should visually provide some form of horizontal separation, therefore foregoing the need to add vertical lines (or making them somewhat superfluous). Your table, moulded into a booktabs environment might look something like this:

\documentclass{article}
\usepackage{graphicx}% http://ctan.org/pkg/graphicx
\usepackage{multirow}% http://ctan.org/pkg/multirow
\usepackage{booktabs}% http://ctan.org/pkg/booktabs
\begin{document}
\begin{tabular}{c@{\qquad}ccc@{\qquad}ccc}
  \toprule
  \multirow{2}{*}{\raisebox{-\heavyrulewidth}{Title}} & \multicolumn{3}{c}{Category~A} & \multicolumn{3}{c}{Category~B} \\
  \cmidrule{2-7}
  & Item~1 & Item~2 & Item~3 & Item~1 & Item~2 & Item~3 \\
  \midrule
  $X$ & 1 & 2 & 3 & 1 & 2 & 3 \\
  $Y$ & 1 & 2 & 3 & 1 & 2 & 3 \\
  \bottomrule
\end{tabular}
\end{document}

You'll notice the use of \toprule, \midrule (\cmidrule) and \bottomrule as complements to the traditional \hline and \cline commands.

I've modified the columns to be all centered c for visual appeal. Additionally, separating the Category headings I've inserted a \qquad separation between the respective columns. Since booktabs also add thicker-than-normal rules, graphicx was required to drop Title a little lower than what the regular multirow package provides with \multirow{2}{*}{...}. This drop was obtained using \raisebox{-\heavyrulewidth}{...}. \heavyrulewidth is a width (or length) definition from booktabs.