Two-Column Articles – Single Column Appendix in Two-Column Article

appendicesarticletwo-column

My article uses the twocolumn parameter of the article document class. However I want to list my images as a multipage appendix at the end of the document (in a new page) but I want a single column appendix so that I can center my figures properly.

I have tried to use the minipage environment inside \twocolumn [ ] but it does not seem to work. Take a look at the code:

%document body, packages etc.
\newpage

\section*{Appendix}
\begin{center}
\begin{minipage}[c]{\textwidth}

\begin{figure}
    \includegraphics[width=\columnwidth]{curve1}
  \caption{An arbitrary initial poinset $\mathbb{S}^2$.}
    \label{curve1}
\end{figure}
%figure curve 1



\end{minipage}


\end{center}
\end{document}

For instance, the figure does not appear to be rendered and the error which is returned by the compiler is:

Not in outer par mode

Best Answer

The error you get is due to the fact that you're embedding a floating environment like figure in a minipage and this is not allowed.

To achieve what you want, when you are in a two-column document, simply issuing the command 

\onecolumn

puts you in one-column mode.

Also, to have centered contents inside the figure, use \centering instead of a center environment.

MWE

\documentclass[twocolumn]{article}
\usepackage[demo]{graphicx}
\usepackage{amssymb}
\usepackage{lipsum} % just for the example

\begin{document}

\section{main}
\lipsum[1-5]

\onecolumn

\section*{Appendix}
\lipsum[1-2]

\begin{figure}[hbt]
  \centering
    \includegraphics[width=\columnwidth]{curve1}
  \caption{An arbitrary initial poinset $\mathbb{S}^2$.}
    \label{curve1}
\end{figure}

\end{document}

Output

enter image description here

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