# How to typeset this symbol?

It's not \mathscr{I}, which is more italic (slanted)

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This looks like a problem for detxify! –  Seamus Jun 23 '11 at 12:09
Have a look at “How to look up a math symbol?” for ideas how you can easily find a particular symbol. –  Martin Scharrer Jun 23 '11 at 12:10
@Seamus: It would be really create if detexify would accept an image URL as input. It's sometimes difficult to draw them correctly. –  Martin Scharrer Jun 23 '11 at 12:12
@Martin yeah I've been trying to draw that for like 3 minutes now! My rollerball mouse is not designed for drawing... –  Seamus Jun 23 '11 at 12:14
I've found something fairly similar in the STIX fonts, but it is more slanted than that and as you specifically say that \mathscr{I} is more slanted then I guess that's not what you want. –  Loop Space Jun 23 '11 at 12:38

\documentclass{standalone}
\pdfmapfile{+rsfso.map}
\DeclareSymbolFont{rsfso}{U}{rsfso}{m}{n}
\DeclareSymbolFontAlphabet{\mathscr}{rsfso}

\begin{document}
$\mathscr{I}$
\end{document}


The \pdfmapfile is necessary as of today, since it seems that the map file doesn't correctly register into TeX Live. Works with TeX Live 2010 and 2011/testing.

The package mathrsfs defines \mathscr to use the font rsfs10 (or another size), while my definition requests the font rsfso10 (or at different size). This font has been developed by Michael Sharpe (texdoc rsfso), but his package redefines \mathcal instead of using a different command. So I copied the definition from mathrsfs changing rsfs in the font names into rsfso.

The font is just like RSFS, but less slanted. I don't know why the TeX Live manager doesn't add the map file to pdftex.map; but since the trick with \pdfmapline works, why bother?

Well, we should bother if the engine used is Xe(La)TeX, so a bug report will be filed.

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That appears to be it.. Could you explain the difference with the results that I (and Herbert) got when using \mathscr{I}? –  willem Jun 23 '11 at 16:00
Works for me now without the pdfmapfile, so apparently the bug got fixed. –  Ben Crowell Dec 26 '13 at 16:37
@BenCrowell I guess so. –  egreg Dec 26 '13 at 16:39

The sensible answer is "find a suitable font" (for example, the STIX script I is pretty close, but is perhaps too slanted). Here's a silly answer.

\documentclass{standalone}
\usepackage{tikz}
\usepackage{calligraphy}

\begin{document}
\begin{tikzpicture}[scale=10]
\calligraphy[copperplate,red,heavy,heavy line width=.2cm,light line width=.1cm]
(0.8,0.51) .. controls +(-.1,-.08) and +(0,-.15) .. (0.5,0.6) .. controls +(0,.15) and +(-.13,-.07) .. (0.85,0.72) +(0,0) .. controls +(-.26,-0.07) and +(.12,.15) .. (0.61,0.3) .. controls +(-.12,-.15) and +(0,-.13) .. (.22,.28);
\end{tikzpicture}
\end{document}


which produces:

Apart from the blob at the end, it's pretty close. I know that it's close because I did it by blowing up the image in the post and drawing on top of it. The line widths probably need tweaking a little, but it's only meant to be a silly answer ...

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NICE! However, I need to use this in a journal article, and I'm not sure if editor's like this stuff.. –  willem Jun 23 '11 at 13:23
You should probably mention that the calligraphy package isn't on CTAN yet and explain where to get it and how awesome it is –  Seamus Jun 23 '11 at 13:32
@willem: I did say it was silly! egreg's answer looks more promising. I have to say that I'm curious as to why \mathscr{I} wouldn't be acceptable to you. –  Loop Space Jun 23 '11 at 13:33
@Seamus: I was counting on the fact that no-one would be silly enough to actually try to do this. –  Loop Space Jun 23 '11 at 13:34

Choose another font if needed.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[charter]{mathdesign}

\begin{document}
\Huge
$\mathfrak{I} \mathscr{I}$

\end{document}


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