Figure in latex

Figure in latex centrate con subfigure

\begin{figure}\label{fig:nome-riferimento}

 \begin{center}

  \subfigure[]{\includegraphics[width=\columnwidth]{images/pdf/error1}}

 \subfigure[]{\includegraphics[width=\columnwidth]{images/pdf/error2}}\\

  \subfigure[]{\includegraphics[width=\columnwidth]{images/pdf/error3}}

  \subfigure[]{\includegraphics[width=\columnwidth]{images/pdf/error4}}\\

 \end{center}

 \caption{caption della figura. (a) punto a. (b) punto b.}

 \end{figure}

Figure su due colonne per articolo con subfigure

\begin{figure*}\label{fig:nome-riferimento}

 \begin{center}

  \subfigure[]{\includegraphics[width=\columnwidth]{images/pdf/error1}}

 \subfigure[]{\includegraphics[width=\columnwidth]{images/pdf/error2}}\\

  \subfigure[]{\includegraphics[width=\columnwidth]{images/pdf/error3}}

  \subfigure[]{\includegraphics[width=\columnwidth]{images/pdf/error4}}\\

 \end{center}

 \caption{caption della figura. (a) punto a. (b) punto b.}

 \end{figure*}