Section numbering style changes when Part I is made Roman

Question

I am writing a book and wish to make the numbering in part I Roman while preserving the numbering style in the Arabic part II. I present as a minimal example below. If the "\renewcommand"s are commented out the numbering is as desired. After Part I is given Roman numbering the wished for nesting disappears. How can I preserve the original format?

    \documentclass[10pt,oneside,usenames,dvipsnames]{book} 
      \setcounter{tocdepth}{2}
    \setcounter{secnumdepth}{2}
\begin{document}
\tableofcontents
\renewcommand{\thechapter}{\Roman{chapter}}
\renewcommand {\thesection}{\Roman{section}}
\renewcommand {\thesubsection}{\Roman{subsection}}

\part{1}
\chapter{FIRST}
\section{First}
\subsection{first}


\renewcommand{\thechapter}{\arabic{chapter}}
\renewcommand {\thesection}{\arabic{section}}
\renewcommand {\thesubsection}{\arabic{subsection}}
\part{2}
\chapter{SECOND}
\section{Second}
Want this numbered as 2.1 which it is until Part I numbering is made Roman. It then appears as just 1. The section numbering style is not as wanted after a Roman Part I.
\subsection{second}
Want Numbering here to be 2.1.1 which it is until Part I numbering is made Roman. It appears as 1. The subsection is numbered but the style is wrong. How can I keep the 2.1.1 style of numbering with a Roman Part I?

\subsubsection{2nd}

Want no numbering here, which works with and without the Roman Part 1.

\end{document}

score 1 · Accepted Answer · answered Jul 10 '20 at 15:31

The nesting can be acheived by including the parent section and a full stop in front of your renewed commands as follows:

\renewcommand{\thechapter}{\Roman{chapter}}
\renewcommand {\thesection}{\Roman{chapter}.\Roman{section}}
\renewcommand {\thesubsection}{\Roman{section}.\Roman{subsection}}

(and similarly when you introduce the arabic numbers)

Section numbering style changes when Part I is made Roman

1 Answers1