# Aligning numbers by decimal points in table columns

Let me begin by stating that I did google the answers (and I'll reference to them soon). Yet each of the resources I found discussed one particular method, I'm interested in a comparison of the approaches.

So far, I've found three ways to deal with this problem:

• split the number into two columns (integer and fractional parts), as documented here or here. The LaTeX code is simple, but the approach is a pain when it comes to copying and pasting tables from external sources.

• use dcolumn manually

• use Mike Zhang's automatic converter (description). I have yet to test it.

What do most people use? dcolumn? Are there other options?

## 2 Answers

The newest option is using the S column type of the siunitx package.

\documentclass{article}

\usepackage{siunitx}

\begin{document}
\begin{tabular}{S[table-format=3.2]}% syntax for siunitx v2; for v1 use "tabformat"
555 \\
7.77 \\
99.9
\end{tabular}

\end{document}


• Indeed, in version 2 of siunitx you will find that there is an implementation that is ~ the same as the dcolumn one, plus a second approach more similar to rccol. – Joseph Wright Sep 4 '10 at 21:48
• This looks great. I can't get it to work though. With pdflatex from texlive 2009 on OSX, I got: ! Package xkeyval Error: table-format' undefined in families key'. – dank Sep 5 '10 at 13:01
• Seems like you're using siunitx v.1.x (the current version is 2). Try tabformat instead of table-format. – lockstep Sep 5 '10 at 13:58
• Just a note: table headers gave me an error, so I had to wrap them in a \multicolumn{1}{c}{name} – daniel kullmann Nov 15 '11 at 10:31
• in response to a comment by daniel kullmann Nov 15 '11 at 10:31 The official way of getting siunitx to ignore bits of text, like headers, is to just wrap them in braces; i.e. {name} will work just as well as \multicolumn{1}{c}{name}. See for instance tex.stackexchange.com/questions/3709/… (would still like newbies to be able to post comments!) – Sam Mason Sep 23 '12 at 17:41

Even though it's already been mentioned in the posting, it's worth discussing the dcolumn package in more detail. The package provides a column type called D that performs alignment on the decimal marker. The D column type takes three inputs: the input decimal marker (usually . or ,), the output decimal marker (again, usually . or ,), and the number of digits before and after the decimal marker. If the input and output decimal markers are always the same -- e.g., always . -- it's useful to set up a short-hand as follows:

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


Here's a full MWE that's based on @lockstep's code -- indeed, with this simple example the outputs of S[table-format=3.2] and D{.}{.}{3.2} are identical :

\documentclass{article}
\usepackage{dcolumn}
\newcolumntype{d}[1]{D{.}{.}{#1}}
\begin{document}
\begin{tabular}{d{3.2}}
555 \\
7.77 \\
99.9
\end{tabular}
\end{document}

• The only difference I see between dcolumn and siunitx is that for column headers composed of text, you can use both \multicolumn{c}{1}{header} or {header} in siunitx whereas in dcolumn, the only option is \multicolumn{c}{1}{header}. This is just a minor thing. – Denis Cousineau Oct 10 '16 at 22:05
• @DenisCousineau - In practice, if you find yourself writing a lot of \multicolumn{1}{c}{...} "wrappers", it pays to set up a shortcut macro, say via \newcommand{\mc}[1]{{\multicolumn{1}{c}{#1}}, so one can type \mc{...}. That's only two more keyboard strokes than {...}. :-) – Mico Oct 10 '16 at 22:12
• @Mico Exactly the MWE which I was looking for! But then you give a guy a hand, he starts getting ideas and wants two arms: 1. I would like to align signed decimal numbers, and 2. for the next to last line, I would like the standard dotted line that says etc. – schremmer Dec 31 '18 at 19:10
• @schremmer - If you want to stay with the dcolumn machinery, you just need to add one extra column for the sign symbol. E.g., to handle numbers such as -1245.56, you'd set d{5.2}. To typeset ... in a d column, just write \multicolumn{1}{c}{\dots} or, using the \mc device I mentioned in a comment above, define the \mc shortcut macro in the preamble and write \mc{\dots} in a table cell. If you need the ultimate in formatting control of numeric data in table cells, do consider using the siunitx package and its S column type, though. – Mico Dec 31 '18 at 23:45
• @Mico Thanks for a prompt answer which works and that even I can understand. But why do $+1.0$, $+10.0$, etc work but $+0.1$, $0.01$, etc right-align, that is the 1s line up? Just a bit curious. But, again, without  everything works fine of course. – schremmer Jan 1 '19 at 4:02