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Suppose you want to denote vectors by upright bold letters; then \mathbf{u} works fine, except that if it's a Greek letter you have to use \boldsymbol{\omega} instead.

Question: Is it possible to define a generic vector command in LaTeX which automatically chooses between \mathbf and \boldsymbol, so that one can write just \vect{u} and \vect{\omega} without having to treat the Greek symbols specially by hand?

(Just to be clear: \newcommand{\vect}[1]{\boldsymbol{#1}} is no good in this situation, since \boldsymbol{u} gives bold italic instead of roman.)

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\boldsymbol(\omega) -> \boldsymbol{\omega}; I couldn't edit because of some "minimum 6 character" rule... –  equaeghe Feb 22 '13 at 15:35
    
@equaeghe: Fixed. –  Hans Lundmark Feb 23 '13 at 8:30
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3 Answers

up vote 13 down vote accepted

You can use both commands together and define something like

\usepackage{bm}
\newcommand{\vect}[1]{\boldsymbol{\mathbf{#1}}}

which should work for most cases.

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The macro

\newcommand{\vect}[1]{\boldsymbol{\mathbf{#1}}}

does not work with mathtime pro lite fonts (and from the comments it appears that it does not work with mathpazo either). Another approach is to simply check if the argument is A-Za-z.

\usepackage{bm,xstring}

\def\VEC#1%
    {\IfSubStr{ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz}{#1}
        {\mathbf{#1}}
        {\bm{#1}}}

This is inefficient since it performs the substring check for each execution. One could define macros \VEC@A, \VEC@B etc (using a simple loop), and then check do

\def\VEC#1%
    {\ifcsname VEC@#1\endcsname
        \mathbf{#1}%
     \else
         \bm{#1}%
     \fi}
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Although this doesn't answer your question, have you tried using the bm package? Then $\bm{\omega}$ gives a bold omega, $\bm{u}$ gives a bold (math italic) u, and $\bm{\mathrm{u}}$ a bold roman u.

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Indeed, defining something like \newcommand{\vect}[1]{\boldsymbol{\mathbf{#1}}} would do the trick. –  Juan A. Navarro Sep 27 '10 at 18:55
    
@Juan: why not make an answer out of your comment? –  Konrad Swanepoel Sep 27 '10 at 19:02
    
Hmm.. because I thought it was pretty much the same (i.e. use both commands together), but maybe not? –  Juan A. Navarro Sep 27 '10 at 19:07
    
@Juan: Thanks, that works! Except that I'm getting weird errors from an \underbrace in a file where I tried it: "Use of \reserved@a doesn't match its definition." and " LaTeX Error: Too many math alphabets used in version bold." Unfortunately that particular formula works fine in a file on its own, so I'm having trouble producing a minimal example where it fails... –  Hans Lundmark Sep 27 '10 at 19:41
    
@Juan: Anyway, if you put your comment in an answer instead I can accept it. –  Hans Lundmark Sep 27 '10 at 19:42
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