Split subfigures over multiple pages

Question

I have the following code for a Figure with 4 subfigures:

\documentclass{article}
\usepackage{graphicx}
\usepackage{caption}
\usepackage{subcaption}

\begin{document}

\begin{figure}[b]
    \centering
    \begin{subfigure}[b]{\textwidth}
        \includegraphics[width=\textwidth]{./plots/arm1.pdf}
        \subcaption{$Q^{*}$ values for arm 1}
        \label{fig:arm1}
    \end{subfigure}
    ~
    \begin{subfigure}[b]{\textwidth}
        \includegraphics[width=\textwidth]{./plots/arm2.pdf}
        \subcaption{$Q^{*}$ values for arm 2}
        \label{fig:arm2}
    \end{subfigure} 
    ~
    \begin{subfigure}[b]{\textwidth}
        \includegraphics[width=\textwidth]{./plots/arm3.pdf}
        \subcaption{$Q^{*}$ values for arm 3}
        \label{fig:arm3}
    \end{subfigure} 
    ~
    \begin{subfigure}[b]{\textwidth}
        \includegraphics[width=\textwidth]{./plots/arm4.pdf}
        \subcaption{$Q^{*}$ values for arm 4}
        \label{fig:arm4}
    \end{subfigure} 
    \caption{$Q^{*}$ values for different arms}
    \label{fig:arms}
\end{figure}

\end{document}

This results in this page

But this way, the 4 subfigures are too large to fit on 1 page. I would like to split this over 2 pages, keeping the subcaptions a, b, ... How can I do this?

Answer 1

Split your figure into two figures and than to the second one immediately after \begin{figure} add command \ContinuedFloat. With this both figures will have the same caption number, however the sub captions numbering is continued from the previous figure:

\documentclass{article}
\usepackage{graphicx}
\usepackage{caption}
\usepackage[skip=0.5ex]{subcaption}

%---------------- show page layout. don't use in a real document!
\usepackage{showframe}
\renewcommand\ShowFrameLinethickness{0.15pt}
\renewcommand*\ShowFrameColor{\color{red}}
%---------------------------------------------------------------%
\usepackage{lipsum}

    \begin{document}
    \lipsum[1]
\begin{figure}[!b]
    \centering
    \begin{subfigure}{0.6\textwidth}
        \includegraphics[width=\linewidth]{example-image}
        \subcaption{$Q^{*}$ values for arm 1}
        \label{fig:arm1}
    \end{subfigure}

\medskip
    \begin{subfigure}{0.6\textwidth}
        \includegraphics[width=\linewidth]{example-image}
        \subcaption{$Q^{*}$ values for arm 2}
        \label{fig:arm2}
    \end{subfigure}
    \caption{$Q^{*}$ values for different arms}
\end{figure}%
\begin{figure}[ht]\ContinuedFloat
    \centering
    \begin{subfigure}{0.6\textwidth}
        \includegraphics[width=\linewidth]{example-image}
        \subcaption{$Q^{*}$ values for arm 3}
        \label{fig:arm3}
    \end{subfigure}

\medskip
    \begin{subfigure}{0.6\textwidth}
        \includegraphics[width=\linewidth]{example-image}
        \subcaption{$Q^{*}$ values for arm 4}
        \label{fig:arm4}
    \end{subfigure}
    \caption[]{$Q^{*}$ values for different arms (cont.)}
    \label{fig:arms}
\end{figure}
    \lipsum[2-3]
    \end{document}