! LaTeX Error: File `\unskip ' not found

Question

I appear to be having a problem with embedding images in a tabular enviroment. I getting the following error:

! LaTeX Error: File `\unskip ' not found.

and here is the offending piece of code. The compiler points me to the line beginning with \multicolumn

\begin{figure}[H]
\centering
  \begin{tabular}{@{}cc@{}}
      \includegraphics[scale=0.22]{lig_nontp_align.png} &
      \includegraphics[scale=0.22]{transporthist.png} \\
    \multicolumn{2}{c}{\includegraphics[width=.23\textwidth]}
  \end{tabular}
  \caption{\textit{Left:} Non-transport and ligand proteins aligned to the ligand HMM model. \textit{Right:} the three different sub-types of transmembrane proteins aligned to the ligand HMM model. }
\end{figure}

I can find problems to do with "\unskip" form googling, but not quite in this capacity. what seems to be the problem?

Thanks.

Answer 1

Your example has \includegraphics[width=.23\textwidth] with no file name. The result will be that \includegraphics will pick up the next thing it finds as the mandatory argument. Inside a LaTeX tabular cell that will be an \unskip (inserted by LaTeX): this needs to be fixed.