Turn on subsection numbering in memoir

Question

It seems that the memoir class automatically avoids numbering subsection headings. Chapter and section titles are numbered, but subsection headings contain only the subsection name, and are not prefixed by the subsection number. Why is this the case, and more importantly, how do I turn subsection numbering back on?

Answer 1

The counter secnumdepth controls "[t]he level number of the least significant sectional unit with numbered headings" (Lamport, LaTeX: A document preparation system , p. 176). The memoir class sets secnumdepth to 1 (section), so you should change this to 2 (subsection). Alternatively, you may use the memoir command \setsecnumdepth.

\documentclass{memoir}

\setcounter{secnumdepth}{2}% alternative A
% \setsecnumdepth{subsection}% alternative B

\begin{document}

\chapter{bla}

\section{blubb}

\subsection{foo}

\end{document}

Answer 2

change the secnumdepth, using the \setcounter{secnumdepth}{2} the following table may help.

Command                            Level        Comment
------------------------------------------------------------------------
\part{part}                        -1       not in letters
\chapter{chapter}                   0       only books and reports
\section{section}                   1       not in letters
\subsection{subsection}             2       not in letters
\subsubsection{subsubsection}       3       not in letters
\paragraph{paragraph}               4       not in letters
\subparagraph{subparagraph}         5       not in letters

Answer 3

The correct way to do this, specifically for memoir, IMO, is to use

\setsecnumdepth{subsection}

Why?:

• It's a higher-level command --- \setcounter is somewhere in the bowels of memoir/LaTeX
• It's semantic --- saying "subsection" is hopelessly more meaningful than saying "2"
• It's practical --- it persists across \mainmatter