Force upright Greek letters with isomath

Question

The isomath package makes it possible to typeset upright Greek letters via \mathrm and \mathbf. Is it it possible to force all Greek letters to be typeset upright unless specified otherwise, e.g. to make it so that \(\Phi \Psi\) delivers the same output as \(\mathrm{\Phi \Psi}\)? An ideal solution would be to load isomath with some option and if it optionally could make difference of upper and lower case Greek letters.

\documentclass{article}

\usepackage{isomath}

\begin{document}

\(\Phi \Psi\)% These are typeset in italic

\(\mathrm{\Phi \Psi}\)% These are typeset upright

\end{document}

Answer 1

You don't need the isomath package:

\DeclareMathSymbol{\Gamma}{\mathalpha}{operators}{0}
\DeclareMathSymbol{\Delta}{\mathalpha}{operators}{1}
\DeclareMathSymbol{\Theta}{\mathalpha}{operators}{2}
\DeclareMathSymbol{\Lambda}{\mathalpha}{operators}{3}
\DeclareMathSymbol{\Xi}{\mathalpha}{operators}{4}
\DeclareMathSymbol{\Pi}{\mathalpha}{operators}{5}
\DeclareMathSymbol{\Sigma}{\mathalpha}{operators}{6}
\DeclareMathSymbol{\Upsilon}{\mathalpha}{operators}{7}
\DeclareMathSymbol{\Phi}{\mathalpha}{operators}{8}
\DeclareMathSymbol{\Psi}{\mathalpha}{operators}{9}
\DeclareMathSymbol{\Omega}{\mathalpha}{operators}{10}

To get an italic Gamma, use \mathnormal{\Gamma}. Try

$\Gamma\mathnormal{\Gamma}\mathbf{\Gamma}$

The command \DeclareMathSymbol is used for assigning a meaning to characters or commands in math mode. The second argument contains the "kind" of symbol; \mathalpha means a symbol that obeys to the alphabet selection commands. The third argument is the alphabet used by default; the fourth is the slot in the font. All the standard declarations are in fontmath.ltx loaded at format creation time.

Notice that these declarations won't work if the default font encoding of the document is T1 instead of OT1, as operators refers to the ordinary Roman document font. One should define a new math alphabet, in this case.

How to do this when the document encoding is T1? One has to define a new symbol font:

\DeclareSymbolFont{otone}{OT1}{cmr}{m}{n}
\SetSymbolFont{bold}{otone}{OT1}{cmr}{m}{n}
\DeclareMathSymbol{\Gamma}{\mathalpha}{otone}{0}
\DeclareMathSymbol{\Delta}{\mathalpha}{otone}{1}
\DeclareMathSymbol{\Theta}{\mathalpha}{otone}{2}
\DeclareMathSymbol{\Lambda}{\mathalpha}{otone}{3}
\DeclareMathSymbol{\Xi}{\mathalpha}{otone}{4}
\DeclareMathSymbol{\Pi}{\mathalpha}{otone}{5}
\DeclareMathSymbol{\Sigma}{\mathalpha}{otone}{6}
\DeclareMathSymbol{\Upsilon}{\mathalpha}{otone}{7}
\DeclareMathSymbol{\Phi}{\mathalpha}{otone}{8}
\DeclareMathSymbol{\Psi}{\mathalpha}{otone}{9}
\DeclareMathSymbol{\Omega}{\mathalpha}{otone}{10}

Of course cmr can be changed into the document's main font family name, provided it contains Greek uppercase letters in its OT1 version; but it's just a matter of giving the correct slot numbers for the chosen font.

Answer 2

isomath was written to set the math style to an 'ISO math style', as the author of the package puts it. Essentially, this means that it will be possible to typeset Greek letters (and non-Greek ones, for that matter) as bold italics, to denote vectors and matrices according to the ISO standard. It is possible to have upright letters, too. isomath requires OML font encoding. The isomath documentation (2011-01-14) states:

Currently only the mathdesign package provides upright fonts in OML encoding.

So, this package also needs to be loaded in order to obtain the correct fonts. LaTeX may otherwise display entirely different characters.

An example based on code snippets from the package documentation could be:

\documentclass[12pt,a4paper]{article}
\usepackage[utopia]{mathdesign}
\usepackage[OMLmathrm,OMLmathbf]{isomath} % options define which alphabets will be loaded, i.e. if bold face font is not necessary, `OMLmathbf` can be ommitted.
\begin{document}
$\Gamma$ $\mathrm{\Gamma}$ $\mathbf{\Gamma}$ $\mathbfit{\Gamma}$

$\pi$ $\mathrm{\pi}$ $\mathbf{\pi}$ $\mathbfit{\pi}$
\end{document}

The output will be:

It seems that the definition of the new math alphabets by isomath can lead to an error. To circumvent this, load the package with the option reuseMathAlphabets.

Known incompatibilities: fourierpackage

Answer 3

An older font with upright Greek letters is AMS Euler. Loading eulervm or eulerpx will also set your Latin letters upright, but some packages have an option like eulergreek to set only the Greek letters to Euler. The stix and stix2 packages support Greek letters in \mathrm. There is also an upright Greek font in fourier. None of these are compatible with isomath or listed in its manual because they use an encoding other than OML.

The lucidamatx package supports math-style=upright. The mathdesign package supports greeklowercase=upright.

The kpfonts and mathdesign packages support the commands \alphaup–\Omegaup. The upgreek package supports \upalpha–\upOmega. Both newtxmath and newpxmath support \upGamma as well as \Gammaup, etc. The fourier package supports \otheralpha–\otherOmega.

If using isomath, you can either load mathdesign and then \usepackage[OMLmathrm]{isomath}, or get the math design fonts with, for example, \usepackage[OMLmathrm, rmdefault=mdput]{isomath} for Math Design Utopia, or load an upright OML math font with \SetMathAlphabet. See table 3 in the isomath manual for the upright families that come in OML. (If you load mathdesign, I would recommend you load erewhon, garamondx or XCharter afterward to fix some bugs with its text fonts.)

I would recommend you use unicode-math in LuaTeX when you can, and legacy math fonts when you have to. All OpenType math fonts contain upright Greek letters that you can use with, for example, \symup{\pi}, \muppi or \uppi. You can also give unicode-math the package option mathrm=sym to make \mathrm{\pi} an alias for \symup{\pi}. If you do so, you should \setoperatorfont and make sure to write \textnormal{iff}, not \mathrm{iff}, for words in math mode. Finally, you can give unicode-math the option math-style=upright.

Answer 4

In fact, the documentation of isomath, Section 2.2.1 (for the 2012-09-04 version), provides several alternatives for setting upright greek letters in math mode. The one I liked the most, because it did not require changing the fonts I was using, was option (e):

e) Use the text character with the alphabeta package from the lgrx bundle:

\usepackage{amsmath}
\usepackage{alphabeta} 

and in the body

$ u = 2 \text{\pi} r $

Edit: As noted by Davislor, it is safer to use \textnormal instead of \text to prevent italics in italicized environments, such as Theorems.

$ u = 2 \textnormal{\pi} r $