How to use siunitx and tabularx together?

Question

I'm using the tabular features of siunitx (for what it is worth: v1.3 since I'm on TexLive 2009) to align numbers in tables, eg.

\begin{tabular}{ p{1.5cm} S S S }
bla & 1.23 & 4.5 & 67.89 \tabularnewline
\end{tabular}

and that works perfectly fine.

Now I would like to have this table span a specific width, or rather to have several tables to have the same width. For this I would normally use tabularx

\begin{tabularx}{\textwidth}{ p{1.5cm} X X X }
bla & 1.23 & 4.5 & 67.89 \tabularnewline
\end{tabular}

Now, is there a way to combine the two? To have the number formatting and alignment features of siunitx inside an automatically resizing table?

Answer 1

The X column in tabularx is then converted to p{<width>} where width is automatically calculated. You can change this by redefining the \tabularxcolumn macro like described in the package manual:

\renewcommand{\tabularxcolumn}[1]{<column definition where #1 is the width>}

The S column uses the c column internally. To replace this with p{<width>} you have to manually place the internal column definition of S into \tabularxcolumn. The following code worked in my tests.

\documentclass{article}

\usepackage{array}
\usepackage{tabularx}
\usepackage{siunitx}


\begingroup
% Allow `_` and `:` in macro names (LaTeX3 style)
\catcode`\_=11
\catcode`\:=11
% Internal code of `S`
\gdef\tabularxcolumn#1{%
    >{\__siunitx_table_collect_begin:Nn S{} }%
    p{#1}%  <- this is different (is `c` in normal `S`)
    <{\__siunitx_table_print:}%
}
\endgroup

\begin{document}

\begin{tabularx}{\textwidth}{p{1.5cm} XXX}
     bla & 1.23 & 4.5  & 67.89 \\
     bla & 1.2  & 4.50 &  7.89 \\
     bla &  .2  &  .50 & 67.8 \\
\end{tabularx}
\end{document}

Answer 2

Taking Martin's solution and re-coding for version 1 of siunitx, you'd do something like

\documentclass{article}

\usepackage{siunitx,tabularx}

\makeatletter
\def\tabularxcolumn#1{%
    >{\si@tab@begin@S[]}%
    p{#1}%  <- this is different (is `c` in normal `S`)
    <{\si@tab@end@S}%
}
\makeatother

\begin{document}

\begin{tabularx}{\textwidth}{p{1.5cm} XXX}
     bla & 1.23 & 4.5  & 67.89 \\
     bla & 1.2  & 4.50 &  7.89 \\
     bla &  .2  &  .50 & 67.8 \\
\end{tabularx}
\end{document}

Answer 3

The quite new tabu package seems to be very encouraging. Section 1.5 of its manual introduces explicitly an example for how to embed siunitx's »S« columns in »X« columns. Regarding tables this package seems to be an allrounder.

Answer 4

Here's a variant of @DavidCarlisle's answer for siunitx version 3:

\documentclass{article}
% \usepackage{array}
\usepackage{tabularx}
\usepackage{siunitx}
\begingroup
% Allow _ and : in macro names (LaTeX3 style)
\catcode\_=11 \catcode:=11
\gdef\tabularxcolumn#1{%
    >{\mode_leave_vertical: \siunitx_cell_begin:w \centering}%
    p{#1}%
    <{\siunitx_cell_end:}%
}
\endgroup
\begin{document}
\noindent
\begin{tabularx}{\textwidth}{p{1.5cm}XXX}
     bla & 1.23 & 4.5  & 67.89 \
     bla & 1.2  & 4.50 &  7.89 \
     bla &  .2  &  .50 & 67.8 \
\end{tabularx}
\end{document}

Also check https://github.com/josephwright/siunitx/issues/423 for improved versions - I removed \ignorespaces to make it compile with \color{red} 4.50, but alignment of colored cells is still off.

Answer 5

No more need to complex hacking, use tabularray package!

With tabularry you can have columns that are at the same time X type (option co=<n>, n is the coefficient for the extendable column, usually 1, but you can use 2 to have a column with double width, etc.) and S type (option si=<settings>).

You don't even have to worry about having non-numeric fields in the S columns, using option guard where needed.

In the following example, I created a new column type A that is both X and S and has the table-format as a parameter. Still, you can also use a Q column directly, specifying all the parameters.

\documentclass[draft]{article}
\usepackage{tabularray}
\UseTblrLibrary{siunitx}
\sisetup{group-digits=false}
\NewColumnType{A}[1][2.2]{Q[si={table-format=#1},c,co=1]}
\usepackage{caption}
\begin{document}
With \texttt{tabularry} you can have columns that are at the same time \texttt{X} type (option \texttt{co=<n>}, where \texttt{n} is the coefficient for the extendable column, usually 1, but you can use 2 to have a column with double width, etc.) and \texttt{S} type (option \texttt{si=<settings>}).
You don't even have to worry about having non-numeric fields in the \texttt{S} columns, using option \texttt{guard} where needed.
\begin{table}[h]
\caption{A table with columns that are X and \texttt
{siunitx} at the same time}
\begin{tblr}{
    colspec={Q[1.5cm]Q[si={table-format=1.2},c,co=1]A[1.1]A},
    row{1}={guard}
    }
    Head 1 & Head 2 & Head 3 & Head 4\
    bla & 1.23 & 4.5 & 67.89\
    bla & 1.23 & 4.5 & 67.89\
    bla & 1.23 & 4.5 & 67.89\
\end{tblr}
\end{table}
\begin{table}[h]
\caption{A table with vertical lines to show the dimension of the columns}
\begin{tblr}{
    colspec={Q[1.5cm]*2{A[1.2]}A},
    row{1}={guard},
    vlines
    }
    Head 1 & Head 2 & Head 3 & Head 4\
    bla & 1.23 & 4.5  & 67.89 \
    bla & 1.2  & 4.50 &  7.89 \
    bla &  .2  &  .50 & 67.8 \
\end{tblr}
\end{table}
\end{document}