我的 tex 文档中有一个子图:
\begin{figure}[!htp]
\centering
\begin{subfigmatrix}{2}
\subfigure{
\includegraphics[width=0.4\textwidth]{img/phi_env_0.pdf}}
\subfigure{
\includegraphics[width=0.4\textwidth]{img/Wannier_R=-5.pdf}}
\subfigure[Bloch function with $k = 1.54$]{
\includegraphics[width=0.4\textwidth]{img/phi_env_1.pdf}}
\subfigure{
\includegraphics[width=0.4\textwidth]{img/Wannier_R=-1.pdf}}
\subfigure{
\includegraphics[width=0.4\textwidth]{img/phi_env_2.pdf}}
\subfigure{
\includegraphics[width=0.4\textwidth]{img/Wannier_R=3.pdf}}
\end{subfigmatrix}
\caption{Baseline accuracy (several classifiers and number of observations).}
\label{fig:bloch_wannier}
\end{figure}
如您所见,这在中间留下了一个很大的空隙。我希望这个空隙消失,然后列居中。我该怎么做?