Table alignment

Question

Consider the following example:

Code

\documentclass{article}

\usepackage{siunitx}
\usepackage{booktabs,dcolumn,array}

\begin{document}

\begin{table}
 \centering
  \begin{tabular}{l !{\quad} c c D{.}{.}{2.2} !{\quad} c c D{.}{.}{2.2}}
   \toprule
    \multicolumn{1}{c!{\quad}}{Times} & \multicolumn{3}{c!{\quad}}{RAAN} & \multicolumn{3}{c}{Dec}\\
   \midrule
     & \si{\hour} & \si{\minute} & \si{\s} & \ensuremath{^\circ} & \ensuremath{\prime} & \ensuremath{\prime\prime} \\
   \midrule
    11{:}40{:}28 & 00 & 03 & 45.48 & 18 & 40 & 03.78 \\
   \bottomrule
  \end{tabular}
\end{table}

\end{document}

Why are s not centered above 45.48 and \prime\prime not centered above 03.78 and how do I achieve this?

Answer 1

dcolumn columns line up entries without a . as if they are integers, so your headings are right aligned to the position of the decimal point in the column. You can use \multicolumn{1} to supply different formatting for the cell:

\documentclass{article}

\usepackage{siunitx}
\usepackage{booktabs,dcolumn,array}

\newcolumntype{d}[1]{D{.}{.}{#1}}

\begin{document}

\begin{table}
 \centering
  \caption{Something.}
  \label{tbl:1}
  \begin{tabular}{l !{\quad} c c D{.}{.}{2.2} !{\quad} c c D{.}{.}{2.2}}
   \toprule
    \multicolumn{1}{c!{\quad}}{Times} & \multicolumn{3}{c!{\quad}}{RAAN} & \multicolumn{3}{c}{Dec}\\
   \midrule
     & \si{\hour} & \si{\minute} & \multicolumn{1}{c !{\quad}}{\si{\s}} & \ensuremath{^\circ} & \ensuremath{\prime} &  \multicolumn{1}{c}{\ensuremath{\prime\prime} }\\
   \midrule
    11{:}40{:}28 & 00 & 03 & 45.48 & 18 & 40 & 03.78 \\
   \bottomrule
  \end{tabular}
\end{table}

This is Table~\ref{tbl:1}.

\end{document}

As an aside since you are loading siunitx anyway you may want to use its S column rather than my dcolumn code.

Answer 2

Here's an implementation with siunitx features:

\documentclass{article}

\usepackage{siunitx}
\usepackage{booktabs,array}

\begin{document}

\begin{table}
\centering
\begin{tabular}{
 c
 S[table-format=2.0,minimum-integer-digits=2]
 S[table-format=2.0,minimum-integer-digits=2]
 S[table-format=2.2,minimum-integer-digits=2]
 S[table-format=2.0,minimum-integer-digits=2]
 S[table-format=2.0,minimum-integer-digits=2]
 S[table-format=2.2,minimum-integer-digits=2]
}
\toprule
Times & \multicolumn{3}{c}{RAAN} & \multicolumn{3}{c}{Dec}\\
\midrule
      & \si{\hour} & \si{\minute} & \si{\s} & \si{\degree} & \si{\arcminute} & \si{\arcsecond} \\
\midrule
11{:}40{:}28 & 00 & 03 & 45.48 & 18 & 40 & 03.78 \\
\bottomrule
\end{tabular}
\end{table}

\end{document}

Instead of adding minimum-integer-digits=2 to each column specifier, a \sisetup{minimum-integer-digits=2} could be made inside the table environment, so it would disappear after it. I just wrote a specifier and copied it five other times, so this is not a big nuisance when typing.

The difference is that if one column doesn't need the setting, the option should be specified. If all S columns share a setting, it may be convenient to use \sisetup.