# Keep chapter number of chapters inserted with \include

Okay, I've puzzled over this for a while and I can't work it out.

I have a document with several chapters, using the memoir class. I've separated each chapter into separate files, and I'm including them using \input.

I did this because at times I may want to produce a file with just chapter 2, or just chapter 3 and not the others. But when I do this, the chapters get renumbered.

How can I make my file customizable, so if I want to, I can make a pdf with just Chapter 2, or just Chapter 3, and no 1?

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You should use \include instead of \input, and then in the preamble say with \includeonly which of the included files you want in your pdf file, like this:

\documentclass{memoir}
\includeonly{chapter1,chapter3}
\begin{document}
\include{chapter1}
\include{chapter2}
\include{chapter3}
\end{document}


The first run(s) of pdflatex should be done without the \includeonly in order to get all the references right.

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On the off-chance that you prefer to \input your chapters rather than \include-ing them, then the solution involves nothing more than redefining the chapter number prior to selectively input-ing your chapters. If that's the path you want to take then here's all you need to do:

\documentclass{memoir}
\usepackage{calc}  % for the arithmetic below

\newcommand*\chapternumber[1]{%
\setcounter{chapter}{#1 - 1}%
}

\begin{document}
\mainmatter
%  \chapternumber{1}\input{chapter1}
\chapternumber{2}\input{chapter2}
\end{document}


I'll leave it to you to work out why the arithmetical adjustment is warranted.

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