Compact tabular alignment on decimal point

Question

I want to align some decimal columns in a tabular on their decimal point. I tried to accomplish this with the dcolumn package, but when I use it as listed in the following, my column width gets bloated that it will not fit on the page (A4).

\usepackage{dcolumn}
\usepackage{hhline, multirow, array, cellspace}
\setlength{\cellspacetoplimit}{3pt}
\setlength{\cellspacebottomlimit}{3pt}
\newcolumntype{.}{D{.}{.}{-2}}
...
{\setlength{\doublerulesep}{1em}
\centering
\begin{tabular}{*{3}{ | Sc | Sc | S. |}}
\hhline{---||---||---}
        \multicolumn{1}{|Sc|}{\multirow{2}{*}{\textbf{Symbol}} } &
    \multicolumn{2}{Sc||}{\textbf{Probability}} &
    \multicolumn{1}{Sc|}{\multirow{2}{*}{\textbf{Symbol}} } &
    \multicolumn{2}{Sc||}{\textbf{Probability}} &
    \multicolumn{1}{Sc|}{\multirow{2}{*}{\textbf{Symbol}} } &
    \multicolumn{2}{Sc|}{\textbf{Probability}} \\ 
\hhline{|~|--||~|--||~|--}
    & \textbf{abs.} & \textbf{rel. [\%]} &
    & \textbf{abs.} & \textbf{rel. [\%]} &
    & \textbf{abs.} & \textbf{rel. [\%]} \\
\hhline{---||---||---}
    A & 22 & 81.16 & J & 3 & 0.16 & S & 34 & 6.32 \\
    B & 104 & 1.49 & K & 58 & 0.77 & T & 33 & 9.05 \\
\hhline{---||---||---}
\end{tabular}}

Without dcolumn alignment:

\begin{tabular}{*{3}{ | Sc | Sc | Sc |}}

With dcolumn alignment:

\begin{tabular}{*{3}{ | Sc | Sc | S. |}}

Can someone please help me to align the decimal values in a compact way?

Answer 1

Two suggestions:

• Place the cell headers -- \textbf{rel. [\%]} -- in \multicolumn{1}{c||}{...} wrappers

• Define a new column type -- say, d -- which takes an argument but otherwise performs alignment on the decimal markers. Using the setup afforded by \newcolumntype{.}{D{.}{.}{-2}} simply doesn't let you achieve really compact numerical columns.

• I would perform alignment on the (implied) decimal markers in the "abs." columns as well.

In the following code, note that the specification for the first pair of decimal-aligned columns is different from those of the other two pairs.

\documentclass{article}
%% simplified code to bare minimum
\usepackage{dcolumn, hhline, geometry}
\newcolumntype{d}[1]{D{.}{.}{#1}}
\renewcommand\arraystretch{1.5}
\begin{document}
\setlength{\doublerulesep}{1em}
\centering
\begin{tabular}{ |c|d{3.0}|d{2.2}| *{2}{ |c|d{2.0}|d{1.2}|} }
\hhline{---||---||---}
Symbol & \multicolumn{2}{c||}{Probability} &
Symbol & \multicolumn{2}{c||}{Probability} &
Symbol & \multicolumn{2}{c|}{Probability} \\
\hhline{|~|--||~|--||~|--}
  & \multicolumn{1}{c|}{abs.} & \multicolumn{1}{c||}{rel.\ [\%]}
& & \multicolumn{1}{c|}{abs.} & \multicolumn{1}{c||}{rel.\ [\%]}
& & \multicolumn{1}{c|}{abs.} & \multicolumn{1}{c|}{rel.\ [\%]} \\
\hhline{---||---||---}
    A & 22 & 81.16 & J &  3 & 0.16 & S & 34 & 6.32 \\
    B & 104 & 1.49 & K & 58 & 0.77 & T & 33 & 9.05 \\
\hhline{---||---||---}
\end{tabular}
\end{document}