Palatino font (newpxmath) misaligns text in fraction numerators

Question

I am using pdflatex in Texmaker (implements TeXLive). Using the default font, the numerator text of the following fractions are aligned to a common baseline:

$$\frac{\partial x}{\partial t} \frac{\partial y}{\partial t} \frac{\partial z_j}{\partial t}$$

However, using the newpxmath package results in the numerators becoming misaligned:

\documentclass{article}
\usepackage{newpxmath}
\begin{document}
$$\frac{\partial x}{\partial t} \frac{\partial y}{\partial t} \frac{\partial z_j}{\partial t}$$
\end{document}

I would like to use New PX for math, but align the numerators as in the default font. I could use \vphantom{...} to force the numerators to have the same height, but is there a more elegant way to do this?

Answer 1

Newer and simpler solution

Since v1.401 of newpxmath (released on October 2, 2019, now available in both MiKTeX and TeX Live), the package offers a new option fracspacing that “modifies fontdimens 8 and 11 of the symbol font to values more appropriate to the newpx fonts”.

\documentclass{article}

% New package option since 2019/10/02 update
\usepackage[fracspacing]{newpxmath}[2019/10/02]

\usepackage{mathtools}% for \clap
\newcommand*\drawbaseline{%
  \clap{\rule{80pt}{0.4pt}}%
}

\begin{document}
\[
\begin{gathered}
x,y\drawbaseline,z\\
\frac{\partial x}{\partial t} \frac{\partial y\drawbaseline}{\partial t} \frac{\partial z_j}{\partial t} \frac{\partial z_{j_j}}{\partial t}\\
\frac{\partial x}{\partial t} \frac{\partial y}{\partial t} \frac{\partial z_j}{\partial t} \frac{\partial z_{j_j}}{\partial t}\\
\end{gathered}
\]
\end{document}

The output looks very similar to the one in the old answer below. The parameters are refined from the very crude 0.8.

---

Old and depreciated answer

The design of Palatino contains long descenders. When a math font is based Palatino, the various math font dimensions should be chosen to avoid unevenness, as much as possible.

There are many font dimensions governing the positions of numerator and denominator in a fraction. We can change two of them in newpxmath which are the most relevant.

\documentclass{article}
\usepackage{newpxmath}

% Code modified from lmsnpxsy.fd
\makeatletter
\expandafter\ifx\csname npxmath@scaled\endcsname\relax
  \let\npxmath@@scaled\@empty%
\else
  \edef\npxmath@@scaled{s*[\csname npxmath@scaled\endcsname]}%
\fi
\DeclareFontFamily{LMS}{npxsy}{\providecommand {\setSYdimens}{}\setSYdimens\skewchar \font =120}
\DeclareFontShape{LMS}{npxsy}{m}{n}{%
  <-> \npxmath@@scaled zplsy
}{%
  \fontdimen 8\font=0.8\fontdimen6\font % was 0.677 of a quad
  \fontdimen11\font=0.8\fontdimen6\font % was 0.686 of a quad
}
\makeatother

\usepackage{mathtools}% for \clap
\newcommand*\drawbaseline{%
  \clap{\rule{80pt}{0.4pt}}%
}

\begin{document}
\[
\begin{gathered}
x,y\drawbaseline,z\\
\frac{\partial x}{\partial t} \frac{\partial y\drawbaseline}{\partial t} \frac{\partial z_j}{\partial t} \frac{\partial z_{j_j}}{\partial t}\\
\frac{\partial x}{\partial t} \frac{\partial y}{\partial t} \frac{\partial z_j}{\partial t} \frac{\partial z_{j_j}}{\partial t}\\
\end{gathered}
\]
\end{document}

Modifying font dimensions gives the most consistent look for all your fractions, but this requires your own aesthetic judgement.

Here, I changed the numerator raising dimension from 0.677 to 0.8 to give more room for long descender. I also changed the denominator dropping dimension from 0.686 to 0.8 for more even spacing both above and below the fraction bar.