[Tex/LaTex] newcolumntype, siunitx, tabu and illegal pream-tokens

siunitxtablestabu

I use tabu with siunitx for making my charts with MikTeX 2.9, tabu 2.8 and now siunitx v2.5g. Since last time using the updater \newcolumn commands like

\newcolumntype D{X[1,c]{%
  S[group-four-digits=true,
  table-format=2.0e1,
  per-mode=symbol]}}
\tabucolumn D

don't work anymore but raise error messages like

Package array Error: Illegal pream-token.

I have no idea how to solve this problem. Can anyone help me?

This is the not-working-anymore minimal example:

\documentclass[a4paper,DIV=12]{scrreprt}
\usepackage[utf8]{inputenc}                 
\usepackage[T1]{fontenc}            
\usepackage[ngerman]{babel}     
\usepackage{siunitx,booktabs}

\usepackage{tabu}
\newcolumntype D{X[1,c]{S[group-four-digits=true,table-format = 2.0e1,per-mode=symbol]}}
\tabucolumn D

\begin{document}
  \begin{tabu} to \linewidth {XDDX}
    \toprule
    one & {two two two two two} & {three three} & four\\
    1.23456 & 1.23456 & 1.23456 & 1.23456 \\
    1.2 & 1.2 & 1.2 & 1.2 \\
    999.9 &999.9 &999.9 &999.9\\
    \bottomrule
  \end{tabu}
\end{document}

Hint: using

\newcolumnD{X[1.c]S[...

(without the curly bracket) as described in other threads does not work, as it is interpreted as columns X and S as substitution for D.

Best Answer

This happens because tabu does something that the LaTeX3 approach specifically forbids: it uses an internal macro from siunitx.

In the revision from v2.5e to v2.5f, the internals of siunitx were marked up as 'private', following the LaTeX3 naming scheme. This does not show up as tabu does a csname-based assignment, and this is silently converted to \relax by TeX. It can be 'fixed' by doing

\ExplSyntaxOn
\cs_new_eq:NN \siunitx_table_collect_begin:Nn \__siunitx_table_collect_begin:Nn
\ExplSyntaxOff

after loading siunitx.

Related Solutions

[Tex/LaTex] Align siunitx numbers in a tabu table

The question was answered by the developer on comp.text.tex and I thought I share it here to answer the question:

Well. In next version, thank to Bruno Le Floch rewritting process, there is no \tabucolumn command:

\newcolumntype Z{ XS[m,
 tight-spacing=true,round-mode=places,
                          round-precision=2] }

X[options]{S[option]} is implemented as XS[ X option , S option] but both still work.

\tabucolumn indeed has no signifiance: I put it there due to some potential parsing problems of the tabu preamble. Problems that no more exist thank to B Le Floch.

XS ( or X[..]{S[...]} ) is always centered: there is no point to set the horizontal alignment for S and s columns: the alignment can't be chosen.

\begin{tabu} to \linewidth {X[l,m,1.2]ZZZZZ}

Avoid X[l,m,1.2] -> for XS columns the comma is "reserved" to separate the options of X with the options for S. Thus it's good practice not to use any delimiter for X options : X [1.2 lm] (and more readable imho)

\hline
 Water vapour*&  18.01534&  -2.418379e+8&  1.886964e+5&
 2.605&  572.4\\
 \hline
\end{tabu}

Now the problem of the vertical alignment: ;-)

The problem is not tabu but siunitx (sorry ;-( ): siunitx leaves too much fixed space before the numbers, because the S column mechanism proceeds with "fixed width". To be able to adjust the spacing, the S column should read the whole tabular and then choose the spacing depending on the "natural length" of each typeset number in each column.

This is what is done inside tabu X, but tabu cannot adjust the spacing made by siunitx: the spaces are inside a box, and tabu can't destroy the box (and thereafter re-align the numbers ! )

If you try with:

 \newcolumntype Z{X[-1
 m]{S[tight-spacing =
 true,round-mode=places,
round-precision=2]}}


 \begin{tabu} to \linewidth {X[lm] |
 *5{Z|}} \hline Water vapour* & 18.01534 & -2.418379e+8 & 1.886964e+5 &
 2.605& 572.4\\ \hline \end{tabu}

There is no more problems of alignment. But the columns width are not the same. You can understand the problem with :

 \newcolumntype Z{S[tight-spacing =
 true,round-mode=places,
 round-precision=2]}

\begin{tabu} to \linewidth {X[-1 lm] |
*5{Z|}} \hline Water \par vapour* & 18.01534 & -2.418379e+8 & 1.886964e+5 &
2.605& 572.4\\ \hline \end{tabu}

This shows that siunitx needs more space than the X coefs allow. Hence the line break inside the X[m] ( ie m ) column.

So: change your margin, or artificially raise the tabu width:

 \newcolumntype Z{X[m]{S[tight-spacing
 = true,round-mode=places,
 round-precision=2]}}
 \hskip-10mm \begin{tabu} to 500pt
 {X[-1 lm] | *5{Z|}} \hline Water \par
 vapour* & 18.01534 & -2.418379e+8 &
 1.886964e+5 &
 2.605& 572.4\\ \hline \end{tabu}

Here there is no more problem. (for future version 2.9 at least)

[Tex/LaTex] Conflict between tabu and tabularx, when using siunitx

tabularx is redefining \arraybackslash (and it even tells in the docu that this is a hack:

\arraybackslash \\ hack.
                 \def\arraybackslash{\let\\\@arraycr}

tabu doesn't like this definition. It expect \arraybackslash to have the meaning from array.sty. So now \\ gives errors. You can give \arraybackslash locally the standard definition back:

 \begingroup
 \def\arraybackslash{\let\\\tabularnewline}
 \begin{longtabu}
  ....
 \end{longtabu}
 \endgroup

Best Answer

Related Solutions

[Tex/LaTex] Align siunitx numbers in a tabu table

[Tex/LaTex] Conflict between tabu and tabularx, when using siunitx

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