\twocolumn undefined control sequence }] [closed]

Question

I am trying to add a figure (a center environment) two a \twocolumn command. I tried this:

\documentclass[10pt,twocolumn]{article}
\usepackage{graphicx}
\usepackage{subfig}

\begin{document}

\twocolumn[{%
\begin{center}
\captiontype{figure}
\subfloat[]
  {
  \fbox{\rule{0pt}{1in} Some text \rule{1in}{0pt} }
  }
\subfloat[]
  {
  \fbox{\rule{0pt}{1in} Some text \rule{1in}{0pt} }
  }
\caption{Our algorithms.}
\end{center}
}] %end twocolumn

\end{document}

but I get "undefined control sequence }]". Any suggestions?

Answer 1

If you're interested in posting an object across two columns in the \twocolumn macro, it should be void of any floats. Here's an option by setting the contents of the two-column spread without resorting to \subfloat. Accurate referencing capability can be incorporated, if needed.

\documentclass[10pt,twocolumn]{article}
%\usepackage{graphicx}% http://ctan.org/pkg/graphicx
%\usepackage{subfig}% http://ctan.org/pkg/subfig
\usepackage{caption}% http://ctan.org/pkg/caption
\usepackage{lipsum}% http://ctan.org/pkg/lipsum

\begin{document}

\twocolumn[{%
\hfill%
\parbox{.4\textwidth}{\centering%
  \fbox{\rule{0pt}{1in} Some text \rule{1in}{0pt} } \\[\abovecaptionskip]
  \small (a)
}%
\hfill%
\parbox{.4\textwidth}{\centering%
  \fbox{\rule{0pt}{1in} Some text \rule{1in}{0pt} } \\[\abovecaptionskip]
  \small (b)
}%
\hspace*{\fill}
\captionof{figure}{Our algorithms.}
%\end{center}
}] %end twocolumn

\lipsum[1-5]

\end{document}

The horizontal alignment is performed using \hfill, while the contents of the "subfloats" are set inside a \parbox. This allows for using a paragraph break (via \\[\abovecaptionskip]).

The caption package provides the caption as needed without being inside a floating environment, while lipsum generates some dummy text.

There are other ways of having a single-column figure (float) in a two-column document (via figure*). Although the placement of such floats might be not what the users wants.