How can I ensure that the four plots (which are all the same size pdfs) appear with the same spacing: see they are offset here:
% Actual versus predicted plots
\begin{figure}[H]
\begin{minipage}[b]{0.45\linewidth}
\centering
\includegraphics[width=\textwidth]{figs/immediate_formula_s_avp.pdf}
\hspace{0.1cm}
\end{minipage}
\begin{minipage}[b]{0.45\linewidth}
\centering
\includegraphics[width=\textwidth]{figs/immediate_formula_s_avp.pdf}
\end{minipage}
\begin{minipage}[b]{0.45\linewidth}
\centering
\includegraphics[width=\textwidth]{figs/immediate_formula_s_avp.pdf}
\hspace{0.1cm}
\end{minipage}
\begin{minipage}[b]{0.45\linewidth}
\centering
\includegraphics[width=\textwidth]{figs/immediate_formula_s_avp.pdf}
\end{minipage}
\caption{Actual Versus Predicted Plots}\label{multiavp}
\end{figure}

subcaptionpackage. That would also fix the minipage problem completely. – percusse Dec 11 '12 at 16:24\phantomcaptioncommand which will hide the individual one to which it is provided but leaves the main caption untouched. – percusse Dec 11 '12 at 16:28[demo]{graphicx}, problem is your second image is not the same size. – yannisl Dec 11 '12 at 16:56\hfillbetween the first two and the second two figures and adding a manual linebreak. Having three\hspaces is weird. I'm not saying it's to blame but it can't help. – Christian Dec 11 '12 at 17:03