How to align integers on the right, but still center them

Question

Suppose we have a table like this:

\begin{tabular}{c}
Heading \\
1 \\
10 \\
100 \\
\end{tabular}

This will center all the numbers. If I want to align them to the right, I could change the column definition to r, but that would but the numbers on the right end of the table. What I would like is for the widest number (in this case 100) to be centered with respect to the column, and the others to be right-aligned to that number. There seem to be a bajillion packages out there that deal in one way or another with aligning numbers by their decimal points, but none seem to offer a simple way to pad numbers to a fixed width. Does anyone have a suggestion?

Answer 1

Using siunitx you'd do

\documentclass{article}
\usepackage{booktabs,siunitx}
\begin{document}
\begin{tabular}{S[table-format=3.0]}
\toprule
{Heading} \\
\midrule
1 \\
10 \\
100 \\
\bottomrule
\end{tabular}
\end{document}

Answer 2

If you want it less complicated then use the \makebox directly for the numbers and \multicolumn for the header.

\documentclass[a5paper]{article}
\usepackage{array,calc}

\newcolumntype{C}{>{\FormatNo} c }
\def\FormatNo\ignorespaces#1\\{%
  \ignorespaces\makebox[\widthof{000}][r]{#1}\tabularnewline}
\begin{document}

\begin{tabular}{C}
\multicolumn{1}{c}{Heading} \\
1 \\
10 \\
100 \\
\end{tabular}

\end{document}

Answer 3

The process can be somewhat automated using eqparbox's \eqmakebox[<tag>][<align>]{<stuff>} and the help of collcell to collect the contents - <stuff> of each cell and pass that to \eqmakebox.

\documentclass{article}

\usepackage{eqparbox,collcell}

\newcommand{\columnalign}{}
\newcommand{\columnalignment}[2]{\renewcommand{\columnalign}{\eqmakebox[#1][#2]}}

\begin{document}

\columnalignment{tag1}{r}

\begin{tabular}{>{\collectcell\columnalign}c<{\endcollectcell}}
  \multicolumn{1}{c}{Heading} \\
  1000 \\
     1 \\
    10 \\
   100
\end{tabular}

\columnalignment{tag2}{r}

\begin{tabular}{>{\collectcell\columnalign}c<{\endcollectcell}}
  \multicolumn{1}{c}{Heading} \\
       words \\
          of \\
   differing \\
      length
\end{tabular}

\end{document}

Note that this requires at least two compilations with every change in the largest element associated with any specific <tag>.

Answer 4

There is no need to use a special LaTeX package. You can use the following standard LaTeX construction with an @-expression:

\documentclass{article}
\begin{document}
\begin{tabular}{r@{\ \ \ \ \ }}
\multicolumn{1}{c}{Heading} \\
1 \\
10 \\
100 \\
\end{tabular}

\end{document}

The drawback is that you need to fiddle with the number of spaces you add to the @-expression.