How to display numbers using comma as a thousands separator?

Question

I want numbers like 5.5 million to be displayed using a comma as a thousands separator as "5,500,000". Is there a way to do this automatically, without having to manually put commas?

Answer 1

I think the siunitx package has this sort of facility.

\num[group-separator={,}]{1234567890}

Should give you 1,234,567,890

Also you can use this as a package option like so: \usepackage[group-separator={,}]{siunitx}

Be warned, this doesn't seem to work with older versions of siunitx

Answer 2

Seamus' answer involving siunitx is the Right Way^TM to do this. That said, it's not so hard to write a simple macro to pretty-print numbers.

\newcount\ppnum
\newcommand\ppnumber[1]{%
        \ppnum=#1\relax
        \ifnum\ppnum<0
                $-$%
                \ppnum=-\ppnum
        \fi
        \let\pptemp\empty
        \loop\ifnum\ppnum>999
                \count255=\ppnum
                \divide\ppnum by1000
                \count255=\numexpr \count255 - 1000*\ppnum \relax
                \edef\pptemp{,\ifnum\count255<100 0\ifnum\count255<10 0\fi\fi
                             \the\count255 \pptemp}%
        \repeat
        \the\ppnum
        \pptemp
}

The first time I wrote this, I used a token register rather than \pptemp, but that required writing \expandafter\expandafter\expandafter{\expandafter... which just seemed excessive.

Edit:
Given that I've now had to fix two bugs in my code, maybe I shouldn't have claimed that it isn't so hard to do this. =)

Answer 3

Using the http://www.ctan.org/pkg/numprint package with \npthousandsep{,} might be an alternative (found after writing the other answer - Murphy's Law!).

Btw: Grouping numbers into pairs of two can be done with the http://www.ctan.org/pkg/telprint package.

Answer 4

The siunitx documentation, v2.3d, 2011/08/18, section 2 Installation, says:

"The package requires LaTeX3 support as provided in the l3kernel and l3packages bundles. [...] LaTeX3, and so siunitx, requires the e-TeX extensions: these are available on all modern TEX systems."

Whenever siunitx/LaTeX3/e-TeX are not available (because one is stuck with something other than a modern TeX system), TH.'s \ppnumber is a great help, if

\count255=\numexpr \count255 - 1000*\ppnum \relax

is replaced by something like (there is no \count254 temporary counter, this is just a pseudo-example!)

\count254 =\ppnum
\multiply\count254 by 1000
\advance\count255 by -\count254 \relax

. TH. said that he deliberately choose

"e-TeX primitive \numexpr because it was slightly shorter"

, but for an alternative to siunitx (in regard of pretty printing numbers) I would suggest going for the most compatible code (even if longer). Additionally, I would suggest replacing

 $-$%

with

\ensuremath{-}%

because \ppnumber might be used in math mode (where the first $ would end the math mode), and I would also suggest

replacing

\newcommand\ppnumber[1]{%

with

\DeclareRobustCommand{\ppnumber}[1]{%

because one never knows whether the command will be used in a way, so that it can break. Further I needed to place a \def\pptemp{} before \newcommand\ppnumber (or before \DeclareRobustCommand{\ppnumber}), otherwise I get a

! Undefined control sequence.
\ppnumber  ...t 253\relax \relax \fi \let \pptemp

As a last thought: \@bsphack \@esphack might be used (requiring \makeatletter and \makeatother, of course). As a very last thought: Replacing , by \thousandseparator and adding

\def\thousandseparator{,}
%\def\thousandseparator{.}
%\def\thousandseparator{\,}

would make it clear that there is flexibility in choosing the separator. (There are languages where the comma is used instead of the period as decimal separator, for example.)

In summary, I got

\makeatletter

\def\thousandseparator{,}
%\def\thousandseparator{.}
%\def\thousandseparator{\,}

\def\pptemp{}
\def\ppnumbersign{}

\DeclareRobustCommand{\ppnumber}[1]{%
\@bsphack
\count255=#1\relax
\ifnum\count255 <0
\def\ppnumbersign{\ensuremath{-}}%
\count255=-\count255\relax
\else
\def\ppnumbersign{\empty}%
\fi
\let\pptemp\empty
\loop\ifnum\count255>999
\edef\ppnc{\the\count255}\relax
\divide\count255 by 1000
\edef\ppna{\the\count255}\relax
\multiply\count255 by 1000
\advance\count255 by -\ppnc
\count255=-\count255\relax
\edef\pptemp{\thousandseparator
\ifnum\count255<100 0
  \ifnum\count255<10 0
  \fi
\fi
\the\count255\pptemp
}%
\count255=\ppna
\repeat
\@esphack%
\ppnumbersign\ppna\pptemp\relax%
}

\makeatother

About count and counter:

http://www.texdev.net/2009/11/17/tex-counts-and-latex-counters/.

Answer 5

sistyle can typeset a wide range of numbers with custom number separators, such as exponential numbers. For example, try:

% preamble
\usepackage{sistyle}
\SIthousandsep{,}

% document
\num{5500000} and \num{5.50e6} are equal.

5,500,000 and 5.50 × 10⁶ are equal.