How can I make the caption of each sub figure like

Question

I have 6 figures, two classes, and want them to be arranged as

Figure 1-C1    Figure 2-C2

(a)               (c)

Figure 3-C1    Figure 4-C2

(b)               (d)

Figure 5-C1    Figure 6-C2

(c)               (e)

Well, I just want to put each class of figures in one column and the caption of them is one followed by another. Not to number them in a horizontal direction.

\documentclass[12pt, a4paper,twoside]{memoir}
    \usepackage{graphicx}
\usepackage{float}            % added on 19112013
\usepackage{colortbl,hhline}  % added on 20112013 for tabular

\begin{document}
\begin{figure}[H]
      \centering
      \subbottom[QMF 02DB2A]{\includegraphics[width=7cm]{chap3/qmf02db3a.jpg}\label{fig319:a}}    \quad
      \subbottom[IQ 02DB2A]{\includegraphics[width=7cm]{chap3/iq02db3a.jpg}\label{fig319:d}}\\

        \subbottom[QMF 04DB1A]{\includegraphics[width=7cm]{chap3/qmf04db1a.jpg}\label{fig319:b}}    \quad
      \subbottom[IQ 04DBA]{\includegraphics[width=7cm]{chap3/iq04db1a.jpg}\label{fig319:e}}\\

        \subbottom[QMF 04DB3A]{\includegraphics[width=7cm]{chap3/qmf04db3a.jpg}\label{fig319:c}}    \quad
      \subbottom[IQ 04DB3A]{\includegraphics[width=7cm]{chap3/iq04db3a.jpg}\label{fig319:f}}
    \caption{Temporary Caption}
    \label{fig319}
    \end{figure}

\end{document}

Answer 1

You can arrange the content inside a tabular or a minipage:

\documentclass{memoir}
\usepackage{graphicx,float}
\newsubfloat{figure}
\newcommand{\tabstrut}{\rule{0pt}{\dimexpr.7\baselineskip+6pt}}
\begin{document}
\begin{figure}[H]
  \centering
  \begin{tabular}{c}
    \subbottom[QMF 02DB2A\protect\tabstrut]{\includegraphics[width=3cm]{example-image-a}\label{fig319:a}} \\
    \subbottom[QMF 04DB1A\protect\tabstrut]{\includegraphics[width=3cm]{example-image-a}\label{fig319:b}} \\
    \subbottom[QMF 04DB3A\protect\tabstrut]{\includegraphics[width=3cm]{example-image-a}\label{fig319:c}}
  \end{tabular} \quad
  \begin{tabular}{c}
    \subbottom[IQ 02DB2A\protect\tabstrut]{\includegraphics[width=3cm]{example-image-b}\label{fig319:d}} \\
    \subbottom[IQ 04DBA\protect\tabstrut]{\includegraphics[width=3cm]{example-image-b}\label{fig319:e}} \\
    \subbottom[IQ 04DB3A\protect\tabstrut]{\includegraphics[width=3cm]{example-image-b}\label{fig319:f}}
  \end{tabular}
  \caption{Temporary Caption}
  \label{fig319}
\end{figure}

\end{document}

\tabstrut helps with the vertical spacing inside a tabular - to obtain the expected 6pt vertical gap provided by \abovecaptionskip.

Answer 2

I have copied this from p48 of the subfig package manual, in the FAQ section:

6.9 “I want my sub-floats to be ordered by column rather than by row, how do I do that?”

The following example shows a schematic for laying out six sub-floats in column order. The only problem with this approach is that, if the floats and their respective captions are not the same height, than the sub-floats will not line up across the page.

\begin{figure}
\begin{minipage}{\columnwidth}
.
.
.
\dots sub-floats (a)--(c) go here.
.
.
.
\end{minipage}
\begin{minipage}{\columnwidth}
.
.
.
\dots sub-floats (e)--(f) go here.
.
.
.
\end{minipage}
\caption{...}
\end{figure}

Does that help?