[Tex/LaTex] Keyval undefined error

beamer

I am new to Beamer. When I run a sample code:

\begin{frame} 
\begin{itemize}
\item Assuming equal power allocation at the source \vspace{0.2cm}
\item Water-filling scheme at the relays over spatial \& temporal domains \vspace{0.1cm}
\item IAPC at each relay puts a lid on the water vessel
\end{itemize}
\begin{columns}[2]
\column{0.4\textwidth}
\begin{itemize}
    \item Relays are rarely used at very low \& high SNRs \vspace{0.2cm}
    \item Stronger relay is used more often \vspace{0.2cm}
\end{itemize}
\column{0.6\textwidth}
\includegraphics[scale=0.4]{Figures/Pon/Pon_naf1_c.eps}
\end{columns}
\end{frame}

I get error: Package keyval Error: 2 undefined \end{frame}. Anyone know what's wrong?

Best Answer

Please always post complete documents, not just fragments. (Here I use draft so the figure is not included)

As noted in comments the error message is telling you that the [2] argument is incorrect, you do not specify the number of columns in beamer.

enter image description here

\documentclass[draft]{beamer}

\begin{document}


\begin{frame}
\begin{itemize}
\item Assuming equal power allocation at the source \vspace{0.2cm}
\item Water-filling scheme at the relays over spatial \& temporal domains \vspace{0.1cm}
\item IAPC at each relay puts a lid on the water vessel
\end{itemize}
\begin{columns}
\begin{column}{0.4\textwidth}
\begin{itemize}
    \item Relays are rarely used at very low \& high SNRs \vspace{0.2cm}
    \item Stronger relay is used more often \vspace{0.2cm}
\end{itemize}
\end{column}
\begin{column}{0.6\textwidth}
\includegraphics[scale=0.4]{Figures/Pon/Pon_naf1_c.eps}
\end{column}
\end{columns}
\end{frame}
\end{document}
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