General ⇒ Numerical values format

[one_eddie]

Does LaTeX enable to format float values or add some sort of custom handler?
I don't event know what should it be

I know I would like to use something like this \format{0.00016493240} and get the output like 1.649324\cdot10^{-4}.

Is there something I could use?

[localghost]

LaTeX is a typesetting system and not a math engine.


Best regards
Thorsten¹

[one_eddie]

You are right, but this is just a matter of seeing the value. So I've thought LaTeX could be able to do that.
Thanks for the lesson. I will write a small program to generate TeX I need.

[T3.]

I know I would like to use something like this \format{0.00016493240} and get the output like 1.649324\cdot10^{-4}.

Is there something I could use?

There are several packages providing such functionality. Take a look at numprint, siunitx and pgf/TikZ and see if any of them suits your needs. PGF even comes with math engine, so you can use it for some simple calculations.

Cheers,

Tomek

[Juanjo]

I haven't been able to find, in the documentation of numprint, siunitx and pgf/TikZ, a command doing exactly what the OP is asking for, so I've defined it. For positive numbers, the function \format in the example below seems to work as expected:

Code: Select all

\documentclass{article}
\usepackage{fp,siunitx}

\newcommand{\format}[2][5]{% format #2 rounding the mantissa to #1 digits (5 by default) 
 \FPln\ExpX{#2}%
 \FPln\lnTen{10}%
 \FPdiv\ExpX\ExpX\lnTen%
 \FPifpos\ExpX% #2 is a number >=1
   \FPtrunc\ExpX\ExpX{0}%
   \FPpow\MantX{10}{\ExpX}%
   \FPdiv\MantX{#2}\MantX%
   \FPround\MantX\MantX{#1}%
 \else% #2 is a number between 0 and 1
   \FPadd\ExpX\ExpX{-1}%
   \FPtrunc\ExpX\ExpX{0}%
   \FPneg\nExpX\ExpX%
   \FPpow\MantX{10}{\nExpX}%
   \FPmul\MantX{#2}\MantX%
   \FPround\MantX\MantX{#1}%
 \fi%
 \num[expproduct=cdot]{\MantX e\ExpX}}

\newcommand{\printexample}[1]{\num{#1} = \format{#1}\par}

\begin{document}

\printexample{1234567.89}
\printexample{123456.789}
\printexample{12345.6789}
\printexample{1234.56789}
\printexample{123.456789}
\printexample{12.3456789}
\printexample{1.23456789}
\printexample{0.123456789}
\printexample{0.0123456789}
\printexample{0.00123456789}
\printexample{0.000123456789}
\printexample{0.0000123456789}

\end{document}

The \num command is defined in siunitx and the \FP ones, in fp. It seems to me that computations done by the fp package are more precise that those done by the math engine provided by pgf/TikZ. There is surely a better way to define \format.

[one_eddie]

Thank you very much.
This is what I was asking about.