A short hyphen in a math formula

Question

In a LyX math formula, I want to write something like "r-number". However, the usual dash looks too long (like a minus sign). I am looking for a short, possibly upper hyphen. I couldn't find it in the lists of symbols in the bottom toolbar, and I also don't know how to search for symbols online If you can give me a tip, how to find a symbol that I need, this will be very useful.

Answer 1

Here are three suggestions. The first is my own, and the second and third are adapted from (http://www.logic.at/staff/salzer/etc/mhyphen/). Note that the first and second both output "math italic" text, but the third outputs "upright" text.

\documentclass{article}
\begin{document}
\newcommand\rnumber{\mathop{\mbox{$r$-$\mathit{number}$}}}
\[
\rnumber(5) = 120
\]
\end{document} 

\documentclass{article}
\usepackage{amsmath}
\mathchardef\mhyphen="2D % Define a "math hyphen"
\begin{document}
\newcommand\rnumber{\mathop{r\mhyphen number}}
\[
\rnumber(5) = 120
\]
\end{document} 

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\newcommand\rnumber{\operatorname{r-number}}
\[
\rnumber(5) = 120
\]
\end{document} 

LyX users should put the definitions (\usepackage, \newcommand, \mathchardef, etc.) in Document -> Settings -> LaTeX Preamble, and the usage (e.g. \rnumber(5) = 120) inside math-mode (Ctrl+M).

Answer 2

I think this is simpler.

$r{\text -}number(5)=120$

Answer 3

My first shot would be \DeclareMathOperator; but it depends on the meaning of "r": if it represents a math variable it should be in italics. I'll show both possibilities, take your pick.

\documentclass{article}
\usepackage{amsmath}

\DeclareMathOperator{\rnumberA}{r-number}
\DeclareMathOperator{\rnumberB}{\mathnormal{r}-number}

\begin{document}

$\rnumberA(2)$

$\rnumberB(2)$

\end{document}

Answer 4

To define a hyphen for use as part of a hyphenated name in a macro, I used the command \def\mymathhyphen{{\hbox{-}}}. This gives the usual en-dash.

Answer 5

Another beautiful dash defined as a symbol. Short and simple.

\documentclass{article}

%Defining my short hyphen with name \mhyphen
%as an ordinary (\mathord) math symbol.
\DeclareMathSymbol{\mhyphen}{\mathord}{AMSa}{"39}

\begin{document}
$r\mhyphen number(t)$
\end{document}

Advantages:

• No extra packages needed.
• No need to change from math to text mode.
• The whole expression r-number(t) needs not be redefined as operator, i.e., \mathop or similars. It affects spacing in formulae.

Answer 6

Yet another way to create a dash is to use a strike-out through a space.

It creates a slightly longer one than given in the answer by Sam Buss, which is what I needed. One could define the macro by

\usepackage[normalem]{ulem}
\newcommand{\mydash}{\hbox{\sout{ }}}