Centering tables in document class apa6

Question

I'm using the apa6 class in doc mode for my thesis.

Now, when I create a table and try to center it on a page, the table is centered alright. The caption, however, still floats on the left of the page where the table used to be.

This what it looks like:

I would like the caption to align with the left side of the table.

This is basicly what my .tex-file looks like:

\documentclass[doc]{apa6}

\usepackage[american,ngerman]{babel}
\usepackage[style=apa,sortcites=true,sorting=nyt]{biblatex}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\shorttitle{Some title}

\begin{document}

\begin{table}[htbp]
    \center
    \caption{Some caption}
    \label{table1}
    \begin{tabular}{lcc}
        \toprule
        Test1 & 1 & 2\\
        Test2 & 1 & 2\\
        Test3 & 1 & 2\\
        \bottomrule
    \end{tabular}
\end{table}

\end{document}

Answer 1

The caption package is loaded by the apa6 class, so you can use its commands to set the caption formatting. Adding:

\captionsetup{justification=centering}

will cause the caption to be centred. However, this doesn't seem to be the exact formatting you want. What you want a left aligned caption aligned to the natural width of the table. As Axel Sommerfeldt notes in the comments, there is an command in the caption package which allows you to place a table and its caption in a box. This will allow you to do what you want quite simply. The command has not yet made it into the documentation of caption (v3.2).

The syntax of this command is:

\captionbox[⟨list entry⟩]{⟨heading⟩}[⟨width⟩][⟨inner-pos⟩]{⟨contents⟩}
\captionbox*{⟨heading⟩}[⟨width⟩][⟨inner-pos⟩]{⟨contents⟩}

(quoting from the subcaption package by the same author:)

The arguments ⟨list entry⟩ & ⟨heading⟩ will be used for typesetting the \caption. ⟨width⟩ is the width of the resulting \parbox; the default value is the width of the contents.

⟨inner-pos⟩ specifies how the contents will be justified inside the resulting \parbox; it can be either c (for \centering), l (for \raggedright), r (for \raggedleft), or s (for no special justification). The default is c. (But you can use any justification defined with \DeclareCaptionJustification as well, e.g. centerlast.)

\documentclass[doc]{apa6}

\usepackage[american,ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\shorttitle{A title}
\begin{document}
Example of a table:

\begin{table}[htbp]
  \centering
  \captionbox{Some caption\label{table1}}{%
    \begin{tabular}{lcc}
        \toprule
        Test1 & 1 & 2\\
        Test2 & 1 & 2\\
        Test3 & 1 & 2\\
        \bottomrule
    \end{tabular}
  }
\end{table}
\end{document}

Unless you have very strict formatting requirements, I would simply stick to centred captions instead of doing this.

(Thanks to both Werner and Axel for their comments on this answer.)

Answer 2

You can load the zref package with the savepos module. This allows you to use \zsavepos{<label>} that saves the (x,y) coordinates of <label> on the page, retrievable via \zposx{<label>} and \zposy{<label>} in scaled points (or sp). This requires at least two compiles.

\documentclass[doc]{apa6}% http://ctan.org/pkg/apa6

%\usepackage[american,ngerman]{babel}% http://ctan.org/pkg/babel
%\usepackage[style=apa,sortcites=true,sorting=nyt]{biblatex}% http://ctan.org/pkg/biblatex
%\usepackage[utf8]{inputenc}% http://ctan.org/pkg/inputenc
%\usepackage[T1]{fontenc}% http://ctan.org/pkg/fontenc
\usepackage[savepos]{zref}% http://ctan.org/pkg/zref

\shorttitle{Some title}

\begin{document}

\begin{table}[htbp]
  \centering
  \begin{minipage}{\dimexpr\zposx{tabR}sp-\zposx{tabL}sp\relax}
    \caption{Some caption}
    \label{table1}
    \zsavepos{tabL}\begin{tabular}{lcc}% Save tabular LEFT coordinate
        \toprule
        Test1 & 1 & 2\\
        Test2 & 1 & 2\\
        Test3 & 1 & 2\\
        \bottomrule
    \end{tabular}\zsavepos{tabR}% Save tabular RIGHT coordinate
  \end{minipage}
\end{table}

\end{document}

You place a label to the left of your tabular environment (say tabL), and one to the right (say tabR). Then, \dimexpr\zposx{tabR}sp-\zposy{tabL}sp\relax gives the exact horizontal distance between tabL and tabR, which you use as the length restriction to a minipage.

You would need a different label for each tabular you want to force this way. It would be possible to automate this procedure by defining your own environment (say) mytable and mytabular, which you would use instead of table.