How to change spacing in array (block matrices)

Question

I want to add a certain spacing s.t. the the partial derivative symbols don't touch the line. Here is the code I have so far.

\begin{align*}
\mathrm{D}_{}F(\textbf{x}_{0}, \textbf{y}_{0}) = 
\left[\begin{array}{c|c}
        \textbf{I} 
  & 0 \\
\hline
        \displaystyle  \frac{\partial f}{\partial \textbf{x}} (\textbf{x}_{0}, \textbf{y}_{0}) &
       \displaystyle \frac{\partial f}{\partial \textbf{y}} (\textbf{x}_{0}, \textbf{y}_{0})
  \end{array}\right]
.\end{align*}

Mico · Answer 1 · 2021-12-02T16:53:59.493

3

I'd like to suggest that you insert a (typographic) strut in a superscript position next to one of the two \partial f expressions.

I would also replace all nine instances of \textbf with \mathbf.

\documentclass{article} 
\usepackage{amsmath} % for '\dfrac' macro
% Define a "tall" typographic strut with no width:
\newcommand\mystrut{{}^{\mathstrut}\kern-\scriptspace} 
\begin{document} 
\[
\mathrm{D}_{}F(\mathbf{x}_{0}, \mathbf{y}_{0}) = 
\left[\begin{array}{@{} c|c @{}}
  \mathbf{I} & 
  0 \\
  \hline
  \dfrac{\partial f\mystrut}{\partial\mathbf{x}} (\mathbf{x}_{0}, \mathbf{y}_{0}) &
  \dfrac{\partial f}{\partial\mathbf{y}} (\mathbf{x}_{0}, \mathbf{y}_{0})
\end{array}\right]
\]
\end{document}

edited Dec 02 '21 at 16:53

answered Dec 02 '21 at 16:43

Mico

506,678

1

A superscript, even if empty, adds a \scriptspace; admittedly, it's 0.5pt, so I can see it only at 1600% magnification on my screen, but there might be situations where this leads to unexpected behaviour. But +1 anyway... – campa Dec 02 '21 at 16:48
@campa - Thanks for this observation. I'll happily append \kern-\scriptspace to the definition of \mystrut. :-) – Mico Dec 02 '21 at 16:53
1

thanks a lot, from now on I will use \mathbf as you recommended! – Descrates Dec 02 '21 at 16:54

score 3 · Answer 2 · answered Dec 02 '21 at 16:45

Here is a solution with cellspace, with adds a minimal vertical spacing at the top & bottom of cells in columns with specifier prefixed with the letter S by default. I took the liberty to remove the align* environment, since nothing is aligned in this formula, and to replace \textbf with the more appropriate ``\mathbf`.

\documentclass{article}
\usepackage{amsmath}
\usepackage[math]{cellspace}
\setlength{\cellspacetoplimit}{3pt}
\setlength{\cellspacebottomlimit}{3pt}
\begin{document}
[ \mathrm{D}{}F(\textbf{x}{0}, \textbf{y}{0}) =
\left[\begin{array}{>{$ \displaystyle}Sc<{$}|>{$ \displaystyle}Sc<{$}}
        \textbf{I}
  & 0 \
\hline
        \frac{\partial f}{\partial \mathbf{x}} (\mathbf{x}{0}, \mathbf{y}{0}) &
       \frac{\partial f}{\partial \mathbf{y}} (\mathbf{x}{0}, \mathbf{y}_{0})
  \end{array}\right]
  ]
\end{document}

thanks a lot for the answer! – Descrates Dec 02 '21 at 16:59 — Descrates, Dec 02 '21 at 16:59
You're welcome. Always glad when I can help! – Bernard Dec 02 '21 at 20:41 — Bernard, Dec 02 '21 at 20:41

Dan · Accepted Answer · 2021-12-02T16:53:55.463

2

Add a \\[-2ex] after \hline

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
\mathrm{D}_{}F(\textbf{x}_{0}, \textbf{y}_{0}) = 
\left[\begin{array}{c|c}
        \textbf{I} 
  & 0 \\
\hline\\[-2ex]%<--
        \displaystyle  \frac{\partial f}{\partial \textbf{x}} (\textbf{x}_{0}, \textbf{y}_{0}) & 
        \displaystyle \frac{\partial f}{\partial \textbf{y}} (\textbf{x}_{0}, \textbf{y}_{0})\\
  \end{array}\right]
.\end{align*}
\end{document}

edited Dec 02 '21 at 16:53

answered Dec 02 '21 at 16:47

Dan

3,699

Thanks, this seems to be the easiest answer! – Descrates Dec 02 '21 at 16:53

score 2 · Answer 4 · answered Dec 02 '21 at 17:01

You need to define a command to add padding below and above its argument as follows

\newcommand{\addstackgapmath}[2][\Sstackgap]{\addstackgap[#1]{$\displaystyle #2$}}

Fot matrices containing horizontal and vertical lines, it is good practice to use bNiceArray

Off-Topic: it is better to enter bold math using \mathbf instead of \textbf

MWE

\documentclass{book}
\usepackage{amsmath}
\usepackage{nicematrix}
\usepackage{stackengine}
\newcommand{\addstackgapmath}[2][\Sstackgap]{\addstackgap[#1]{$\displaystyle #2$}}
\begin{document}
\begin{equation}
    \mathrm{D}{}F(\mathbf{x}{0}, \mathbf{y}{0}) = 
    \left[\begin{array}{c|c}
        \mathbf{I} 
        & 0 \
        \hline
        \addstackgapmath{\frac{\partial f}{\partial \mathbf{x}} (\mathbf{x}{0}, \mathbf{y}{0})} &
        \addstackgapmath{\frac{\partial f}{\partial \mathbf{y}} (\mathbf{x}{0}, \mathbf{y}_{0})}
    \end{array}\right]
.\end{equation}
\begin{equation}
    \mathrm{D}{}F(\mathbf{x}{0}, \mathbf{y}{0}) =
    \begin{bNiceArray}[hvlines-except-borders,margin]{c c}
        \mathbf{I} 
        & 0 \
        \addstackgapmath{\frac{\partial f}{\partial \mathbf{x}} (\mathbf{x}{0}, \mathbf{y}{0})} &
        \addstackgapmath{\frac{\partial f}{\partial \mathbf{y}} (\mathbf{x}{0}, \mathbf{y}_{0})}
    \end{bNiceArray}.
\end{equation}
\end{document}

How to change spacing in array (block matrices)

4 Answers4