How do you get \mathbb{1} to work (characteristic function of a set)?

Question

I am trying to get the digit one printed the \mathbb{} font in math mode, however the command

\mathbb{1}

outputs some rubbish. I certainly saw the character I am after in some pdf's generated from latex, hence my question: how do you get it to work?

The \mathbb provided as part of the amsfonts package does not provide numerals. Section 3.3 of amsfonts' documentation states that the \mathbb command it provides uses the msbm font and so supports only uppercase letters: no lowercase, no numerals. — mas, Aug 27 '11 at 15:52
note that using any package that provides a complete blackboard bold font overrides the \mathbb provided by amsfonts. if you wish to replace only the digit "1", you can use the method described here: Importing a single symbol from a different font — barbara beeton, Feb 13 '17 at 17:30
off topic: After years reading math texts, I think that the most common notation for the characteristic function of a set $A$ is \chi_A. — Sigur, Feb 27 '18 at 11:25
How come "they" don't fix this? Is there a fundamental problem? — Alec Jacobson, Jan 20 '20 at 04:41

score 274 · Accepted Answer · edited Feb 27 '24 at 22:18

274

Since \mathbb doesn't support digits (with amssymb or txfonts) you may use bbm:

\documentclass{article}
\usepackage{bbm}
\begin{document}
\[ \mathbbm{1} \]
\end{document}

bbm example

or dsfont in the doublestroke package:

\documentclass{article}
\usepackage{dsfont}
\begin{document}
\[ \mathds{1} \]
\end{document}

dsfont example

edited Feb 27 '24 at 22:18

user202729

7,143

answered Aug 27 '11 at 14:58

Stefan Kottwitz

231,401

12

I guess \mathbbm{1}is the best in terms of consistency with \mathbb. – Alfredo Hernández Nov 28 '14 at 23:15
1

You can also add \newcommand{\1}[1]{\mathds{1}\left[#1\right]} to your preamble to create a quick indicator function that handles what you wanna put inside it. – Guilherme Salomé Nov 08 '16 at 23:07
I get the error: File bbm.sty not found. Also File dsfont.sty not found. – Albert May 10 '20 at 16:28

Davislor · Answer 2 · 2021-02-16T11:51:55.043

Playing some necromancy here, the answer looks very different in 2021. I especially advise against using bbm, as the accepted answer suggests, since the old-fashioned font format it loads will come out pixelated in a PDF, and nobody prints DVIs out on paper any more.

I’d recommend using unicode-math in LuaTeX when you can, and legacy fonts when you have to. Nearly all OpenType math fonts support \mathbb{1} and \Bbbone out of the box. Few if any come with a bold version that supports \boldsymbol{\mathbb{1}}, but you can fake it if you need it:

\documentclass{article}
\tracinglostchars=2
\usepackage{unicode-math}
\setmathfont{NewCMMath-Book}
\setmathfont{NewCMMath-Book}[
  version=bold,
  FakeBold = 1.2 ]
\begin{document}
[ \mathbb{1} \boldsymbol{\mathbb{1}}
]
\end{document}

If your publisher still requires you to use PDFTeX, or you should wish to, the mathalpha package provides a consistent interface for loading and scaling math alphabets, including blackboard bold and bold blackboard bold. Here are the options that ship with TeX Live and at least partially work:

(Note that you do not need to define \Bbbbone this way in your own document! I put this in the template to simplify testing.)

\documentclass{article}
\usepackage{amsmath}
\usepackage[bb=dsserif]{mathalpha}
\usepackage{bm}
\pagestyle{empty}
\newcommand\Bbbbone{%
  \ifdefined\mathbbb%
    \mathbbb{1}%
  \else%
    \boldsymbol{\mathbb{1}}%
  \fi}
\begin{document}
[ \mathbb{1} \Bbbbone
]
\end{document}

The dsserif alphabet is the only free one I know of that supports both blackboard-bold and bold-blackboard-bold digits in Type-1 format, and that a package can load without changing your other fonts. You will probably want to scale this to match your math font, with the bbscaled= package option.

With bb=pazo instead of bb=dsserif:

With bb=fourier:

With bb=esstix:

With bb=boondox:

There are other legacy packages not available through mathalpha (as of February 2021). Here are some of the more important ones that have not already been mentioned.

The cmathbb package is an attractive outline font based on Computer Modern bold.

With \usepackage[varbb]{newtxmath}, you get the same alphabet as in Xovee’s answer, but replacing the standard \mathbb:

There is a similar option for newpxmath (although this is incompatible with bm).

\documentclass{article}
\usepackage{amsmath}
\usepackage[varbb]{newpxmath}
\pagestyle{empty}
\newcommand\Bbbbone{%
  \ifdefined\mathbbb%
    \mathbbb{1}%
  \else%
    \boldsymbol{\mathbb{1}}%
  \fi}
\begin{document}
[ \mathbb{1} \Bbbbone
]
\end{document}

There is yet another blackboard bold alphabet available through newtxmath and newpxmath, with the vvarbb package option:

The stix and stix2 packages load an alphabet similar to boondox. (Which is a fork of the STIX fonts.) Here is what you get with \usepackage{stix2} instead of mathalpha:

Thank you very much for the answer. However, using unicode-math ruins the other mathbb letters. Is there any way of keeping the standard mathbb while using unicode-math? PS: I keep coming back to this question since I haven't still a satisfactory answer — Manza, Nov 24 '22 at 18:04
@Manza yes, you can \DeclareMathAlphabet with the AMS bb font. Just use another name than \mathbb. — Davislor, Nov 24 '22 at 22:38
@Manza Or load an Opentype font whose \mathbb you like better with range=bb. — Davislor, Nov 24 '22 at 22:38
Btw, the newer version of NewCM provides blackboard math in CM style, similar to dsfont. It contains numbera as well. — Apoorv Potnis, Feb 06 '24 at 15:48

user41766 · Answer 3 · 2014-03-18T21:07:53.133

25

Another option is to use bbold package.

\documentclass{article}
\usepackage{bbold}
\begin{document}
\[ \mathbb{1} \]
\end{document}

bbold example

Though it ruins the letters.

edited Mar 18 '14 at 21:07

answered Mar 10 '14 at 20:16

user41766

489

score 21 · Answer 4 · answered Feb 27 '18 at 09:59

21

I'm surprised no one has mentioned this, but you can use the unicode-math package. Note that you need Xe(La)TeX or LuaLaTeX to use this package.

\documentclass{article}

\usepackage{amsmath}
\usepackage{unicode-math}

\begin{document}
    $\mathbb{1}$
\end{document}

answered Feb 27 '18 at 09:59

Hameer Abbasi

605

Perhaps because it can't be used with pdflatex: "Package unicode-math Error: Cannot be run with pdfLaTeX!" – user26800 May 24 '20 at 16:53
1

Only this worked for me with LuaLaTex. – Evgeny Kuznetsov Jun 05 '20 at 13:34

Xovee · Answer 5 · 2023-03-22T11:12:57.270

15

A new solution: use newtxmath package.

With code:

\usepackage{newtxmath}
$\vmathbb{ABCDEFGHIGKLMNOPQRSTUVWSYZ}$
$\vmathbb{abcdefghijklmnopqrstuvwxyz}$
$\vmathbb{0123456789}$

which results:

Also, this solution is compatible with the ACM Template's whitelist restriction, since there're no need to import other packages, the document class asmart already imported the newtxmath.

Here's the document of the newtxmath: http://ctan.mirror.colo-serv.net/fonts/newtx/doc/newtxdoc.pdf

edited Mar 22 '23 at 11:12

answered Mar 15 '20 at 01:59

Xovee

196

4

Why the lower case letters (except k) are not supported? – Hosein Rahnama Mar 15 '20 at 19:56
This also works with the newpxmath package, could you update you answer? :) – G.J Mar 21 '23 at 10:14
1

@HoseinRahnama now it supports lower letters – Xovee Mar 22 '23 at 11:13
@G.J I have updated the answer! Thank you for remind. – Xovee Mar 22 '23 at 11:14

Marcello Fonda · Answer 6 · 2022-06-19T17:05:06.977

Like user41766 said, using bbold is a good idea (the best imho if unicode-math isn't an option), but it would "ruin" the other letters. You can solve this issue by declaring a new alphabet, importing \mathbb from bbold into your own math alphabet, like was suggested here:

\DeclareMathAlphabet{\mathmybb}{U}{bbold}{m}{n}
\newcommand{\1}{\mathmybb{1}}

Note that you can then use \mathmybb in any other situation and name it any other way you please.

Edit: This question is also nicely dealt with here, where this compact solution can be found to avoid creating a whole math alphabet:

\newcommand*{\boldone}{\text{\usefont{U}{bbold}{m}{n}1}}

Thank you! the above \boldone plus the {bbold} package seem nice to me. — Martin Mächler, May 12 '23 at 11:09

score 2 · Answer 7 · edited Apr 22 '18 at 12:35

This worked for me:

\usepackage{mathbbol}

+\mathbb{1}+

Actually, I'm using LyX, so I put \usepackage in the preamble and then simply used \mathbb with a 1 inside a formula box. It still displays as `rubbish' but renders fine as PDF.

If you don't like the discordance in LyX, you can say something like

\def\bbone{\mathbb{1}}

in the preamble, and then use \bbone in your document, or variants on this theme.

My 2c.

score 2 · Answer 8 · answered Jun 19 '22 at 20:47

Almost all Unicode math fonts have the character U+1D7D9 with TeX control sequence \Bbbone which looks like this: .

If you have Unicode math font loaded then you can use \Bbbone or directly . For example, in OpTeX:

\fontfam[lm]  % loads Unicode math
$\Bbbone$ or $$.

\bye

Jotazuma · Answer 9 · 2017-02-13T16:21:49.390

0

\documentclass{article}        
\usepackage{anyfontsize}         
% For documents in 10pt, 11pt or 12pt     
% \def\one{\mbox{1\hspace{-3.85pt}\fontsize{11}{14.4}\selectfont\textrm{1}}} % 10pt    
\def\one{\mbox{1\hspace{-4.25pt}\fontsize{12}{14.4}\selectfont\textrm{1}}} % 11pt    
% \def\one{\mbox{1\hspace{-4.75pt}\fontsize{13}{14.4}\selectfont\textrm{1}}} % 12pt    
\begin{document}    
You can use either $\one$ or $\one\{A\}$ or $\one_{A}$.
\end{document}

edited Feb 13 '17 at 16:21

answered Feb 12 '17 at 16:16

Jotazuma

25

Welcome to TeX.SE. Do note that \rm is considered deprecated for a LaTeX document. It also doesn't take an argument; instead, it acts as a switch. Thus, instead of \rm{\fontsize{11}{14.4}\selectfont 1}, do write \fontsize{11}{14.4}\selectfont\textrm{1}. Also, is there something that can be done to produce less of an overlap/clash between the tops of the two 1 numeral? – Mico Feb 12 '17 at 16:27
The correct metrics depend on the font and font family, I guess. I typeset most of my documents with \usepackage{mathptmx}, a Times like font, and the code given works just perfectly. Adjust the argument of \hspace accordingly. – Jotazuma Feb 12 '17 at 17:19

D0r1an · Answer 10 · 2024-01-06T19:21:49.540

0

With unicode-math (requires LuaTeX or XeTex), you can change the font of only the \mathbb{} numbers to, e.g., "Latin Modern Math", which does include them:

\setmathfont{Latin Modern Math}[range=bb/{num}]

edited Jan 06 '24 at 19:21

answered Jan 06 '24 at 19:21

D0r1an

1

How do you get \mathbb{1} to work (characteristic function of a set)?

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