How to set the precision in numbers

Question

I include the number as \num{0.12368455}. I need to print '0.1237'.

How to do this...

Answer 1

With the the siunitx package you can use the option round-mode=places, round-precision=4 to obtain the desired results.

1. If you only need to control the rounding for a few numbers you use it as an option to \num:

   

   \documentclass{article}
   \usepackage{siunitx}
   \begin{document}
   \num{0.12368455}
   
   \num[round-mode=places,round-precision=4]{0.12368455}
   \end{document}
   

2. If you need to do this for the entire document you can use \sisetup{round-mode=places,round-precision=4} so that this formatting is applied for the entire document:

   

   \documentclass{article}
   \usepackage{siunitx}
   \sisetup{round-mode=places,round-precision=4}
   
   \begin{document}
      \num{0.12368455}
   \end{document}
   

3. Another way of achieving this is to use round-mode=figures, round-precision=4.

   

   \documentclass{article}
   \usepackage{siunitx}
   
   \begin{document}
       \num[round-mode=figures,round-precision=4]{0.12368455}\par
       \num[round-mode=figures,round-precision=4]{0.12}\par
       \num[round-mode=places,round-precision=4]{0.12368455}\par
       \num[round-mode=places,round-precision=4]{0.12}
   \end{document}
   

round-mode=figures vs round-mode=places

With [round-mode=figures,round-precision=4] you get 4 significant figures, and with [round-mode=places,round-precision=4] you get 4 decimal places. Here is a comparison:

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Similar results can also be achieved using \pgfmathprintnumber:

Code:

\documentclass{article}
\usepackage{pgf}

\newcommand*{\MyNum}[1]{%
    \pgfmathprintnumber[
        fixed,
        precision=4,
        fixed zerofill=true,
        ]{#1}}%

\begin{document}
\MyNum{0.12368455}\par
\MyNum{0.12}
\end{document}