How does one create, caption, label and refer to a subfigure?

Question

So its a fairly simple question to a problem people normally experience. I have a rough idea of what to do, but I am looking for the correct way of doing things. So in the solution I will include what would be the bare minimum requirements I think would get this problem solved. I am looking for feedback and corrections though.

So please tell me, how does one go about creating subfigures within a figure. After that, caption it. Then label it for reference and then refer to it in the text?

Answer 1

The subcaption package provides three ways to build your subfigures:

1) Using the \subcaption command inside, for example, minipages; the syntax:

\subcaption[<list entry>]{<document caption>}

2) Using the subfigure environment.

3) Using the \subcaptionbox command. The syntax:

\subcaptionbox[<list entry>]{<document caption>}[<width>][<inner-pos>]{<contents>}

where <width> is the width of the resulting \parbox; the default value is the width of the contents. <inner-pos> specifies how the contents will be justified inside the resulting \parbox; it can be either c (for \centering), l (for \raggedright), r (for \raggedleft), or s (for no special justification). The default is c.

Here's a little example, illustrating the three approaches, and the use of \ref and \subref to cross-reference the (sub)figures:

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

\begin{document}

\begin{figure}
\begin{minipage}[b]{.5\linewidth}
  \centering
  \rule{3cm}{1cm}% to simulate a figure
  \subcaption{Test subfigure one}
  \label{fig:sub11}
\end{minipage}%
\begin{minipage}[b]{.5\linewidth}
  \centering
  \rule{3cm}{1cm}% to simulate a figure
  \subcaption{Test subfigure one}
  \label{fig:sub12}
\end{minipage}
\caption{A figure with two subfigures}
\label{fig:testfig1}
\end{figure}

\begin{figure}
\begin{subfigure}[b]{.5\linewidth}
  \centering
  \rule{3cm}{1cm}% to simulate a figure
  \subcaption{Test subfigure one}
  \label{fig:sub21}
\end{subfigure}%
\begin{subfigure}[b]{.5\linewidth}
  \centering
  \rule{3cm}{1cm}% to simulate a figure
  \subcaption{Test subfigure one}
  \label{fig:sub22}
\end{subfigure}
\caption{Another figure with two subfigures}
\label{fig:testfig2}
\end{figure}

\begin{figure}
  \centering
  \subcaptionbox{Test subfigure one\label{fig:sub31}}[4cm]{\rule{3cm}{1cm}}%
  \subcaptionbox{Test subfigure two\label{fig:sub32}}[4cm]{\rule{3cm}{1cm}}
  \caption{Another figure with two subfigures}
  \label{fig:testfig3}
\end{figure}

As we can see in Figure~\ref{fig:sub22}...

Subfigure~\subref{fig:sub32} of Figure~\ref{fig:testfig3} shows...

\end{document}

Answer 2

You can use the floatrow package like in Vertically align subfloats at the top while having subcaptions vertically aligned below the subfloats.

\documentclass{article}

\usepackage{tikz}
\usepackage{caption}
\usepackage{subcaption}
\usepackage{floatrow}

\begin{document}

\begin{figure}
\ffigbox
{%
  \begin{subfloatrow}
    \ffigbox
    {%
      \begin{tikzpicture}
        \draw circle (1.25cm) {};
      \end{tikzpicture}%
    }
    {%
      \subcaption{Small circle}%
      \label{fig:c:sc}%
    }
    \ffigbox
    {%
      \begin{tikzpicture}
        \draw circle (2cm) {};
      \end{tikzpicture}%
    }
    {%
      \subcaption{Big circle}%
      \label{fig:c:bc}%
    }
  \end{subfloatrow}
}
{%
  \caption{Circles}%
  \label{fig:c}%
}
\end{figure}

See the circles in Figure~\ref{fig:c}. There is a small circle, \ref{fig:c:sc}, and a big circle, \ref{fig:c:bc}.

\end{document}

Answer 3

You can use the subfig package for this. For a brief guide on how to use it, including captioning, labeling and referencing, have a look at the excellent LaTeX WikiBook section covering it.