# How to convert a one digit number to a two digit number

I have a table that represents a timetable for bus, so each cell contains time of departure as hour followed by minute, both as two digits, but sometimes I don't have two digits,just one so I have to switch eg. from 12 4 -> 12 04. How is it possible?

-
If you add a small usage example which shows the exact use-case people will be able to help you better. How do you get/import the data? –  Martin Scharrer May 17 '12 at 10:02
Very related is How to output a counter with leading zeros? –  Werner May 17 '12 at 22:50

You can define a macro as follows:

\newcommand\twodigits[1]{%
\ifnum#1<10 0#1\else #1\fi
}

\twodigits{12}  % 12
\twodigits{4}   % 04
\twodigits{123} % 123


This macro is fully expandable.

If you also want to cut trailing zeros you can use:

\newcommand\twodigits[1]{%
\ifnum#1<10 0\number#1 \else #1\fi
}

\twodigits{004} % 04


If you want to change a tabular cell from 12 4 to 12 04 without adding explicit macros you can use the collcell package to collect the cell content and feed it to a macro which splits the numbers by the space:

% preamble:
\newcommand\formatdate[1]{\formatdatei#1\relax}
\def\formatdatei#1 #2\relax{%
\twodigits{#1} \twodigits{#2}%
}

\usepackage{collcell}

% later
\begin{tabular}{l>{\collectcell\formatdate}l<{\endcollectcell}}
Bus date  & 12 4 \\
\end{tabular}


If you post a real usage example I can help me with more specific macros.

-
Thank you for response. Can you please take a look here? I've added the question before with a case usage, but someone suggested to post a different question regarding this problem. –  Ion Morozan May 17 '12 at 10:46
@IonMorozan: In such cases always add a link to the other question in the new question. –  Martin Scharrer May 17 '12 at 10:48
Yes you are right! It's is my third post on a forum, so I have to learn. Thank you for the feedback and by the way your solution works great for me. Thank you again! –  Ion Morozan May 17 '12 at 10:51
@MarcoDaniel: Thanks for pointing this out. I wrote the answer under my Windows installation were I don't have LaTeX installed, so I couldn't test it right away. I added a version which handles this kind of input without an assignment. –  Martin Scharrer May 17 '12 at 12:50
@MartinScharrer: I found the following definition in latex.ltx ;-) \def\two@digits#1{\ifnum#1<10 0\fi\number#1} –  Marco Daniel May 17 '12 at 13:18

You can do that using the siunitx package

\documentclass[a4paper,twoside,10pt]{article}

\usepackage{siunitx}

\begin{document}
\num[minimum-integer-digits = 4]{123}
\num[minimum-integer-digits = 4]{4}
\end{document}


prints

0123 0004


or alternatively you can declare the option as default,

\documentclass[a4paper,twoside,10pt]{article}
\usepackage{siunitx}

\begin{document}
\sisetup{minimum-integer-digits = 4}
\num{12}
\num{34}
\end{document}

-
Can you set minimum-integer-digits separately, as a default? –  Brent.Longborough May 17 '12 at 11:56
@percusse thanks for the edit, wasn't in front of a computer all day long.. –  Andreas Wallner May 17 '12 at 22:35

You can also use the xstring package to add the leading zero for single digits:

## Code:

\documentclass{article}
\usepackage{xstring}
\newcommand*{\TwoDigit}[1]{%
\IfStrEqCase{#1}{%
{1}{0}%
{2}{0}%
{3}{0}%
{4}{0}%
{5}{0}%
{6}{0}%
{7}{0}%
{8}{0}%
{9}{0}%
}#1%
}%
\begin{document}
123 $\to$ \TwoDigit{123}

12 $\to$ \TwoDigit{12}

2 $\to$  \TwoDigit{2}
\end{document}

-

You can use LaTeX's internal \two@digit for formatting:

\documentclass{article}
\makeatletter
\newcommand{\twodigit}[1]{\two@digits{#1}}
\makeatother
\begin{document}

\twodigit{12} \par % 12
\twodigit{4} \par  % 04
\twodigit{123}     % 123

\end{document}

-