printf-style number formatting in LaTeX

Question

Is there a way to use printf-style number formatting strings in Latex like %.3f, %d, etc? I'm loading some data from csv files using the datatool package and would like to have it displayed exactly to my specifications.

Answer 1

I've no idea about datatool. siunitx provides some functions to round numbers. See manual of siunitx: 5.4 Parsing numbers, 5.5 Post-processing numbers

For example:

\documentclass{article}
\usepackage{siunitx}

\begin{document}

\begin{tabular}{S[round-mode=places,round-precision=2]}
10. \\
10.1 \\
10.12 \\
10.123 \\
10.1234 \\
\end{tabular}

\end{document}

It gets:

10.00
10.10
10.12
10.12
10.12

Answer 2

If you are willing to use LuaTeX

\directlua{tex.print(string.format("\string\%0.3f", 10.1234567))}

string.format accepts all the usual printf style arguments. The \string\% is needed because % has a special meaning in TeX.

ConTeXt provides a few helper functions so that the above can be written as

\ctxlua{context("\%0.3f", 10.12345)}

If you want, you can easily wrap the above in a macro:

\def\truncate#1#2%
    {\directlua{tex.print(string.format("\string\%0.#1f", #2))}}

or in ConText as

\def\truncate#1#2{\ctxlua{context("\%0.#1f", #2)}}

and then use

\truncate{3}{10.123456}