3

In this code

\documentclass{book}
\usepackage{mathtools}
\usepackage{stix}
\usepackage{multicol,multirow}

\newcommand{\Tonde}[1]{\left(#1\right)}

\newcommand*{\Scale}[2][4]{\scalebox{#1}{$#2$}}%
\newcommand*{\Resize}[2]{\resizebox{#1}{!}{$#2$}}%

\begin{document}

\begin{equation}\label{A_MEG_Blocchi}
A^{(\:\:)}\coloneqq\Tonde{\begin{array}{c|c}\multicolumn{2}{c}{}\\\cline{2-2}&K\end{array}}=
\Tonde{\begin{array}{ccc|ccc}a_{11}^{(1)}&\cdots&\cdots&\cdots&\cdots&a_{1n}^{(1)}\\0&\ddots&\ddots&\cdots&\cdots&\vdots\\\vdots&\ddots&a_{k-1,k-1}^{(k-1)}&\cdots&\cdots&a_{k-1,n}^{(k-1)}\\[2mm]\cline{4-6}0&\cdots&0&a_{kk}^{(k)}&\cdots&a_{kn}^{(k)}\\[2mm]\multicolumn{3}{c}{\multirow{3}{*}{$\mathop{\Scale[5]{0}}$}}&\vdots&\ddots&\vdots\\&&&a_{nk}^{(k)}&\cdots&a_{k+1,n}^{(k)}\\[2mm]\end{array}}
\end{equation}

\end{document}

I'd like to have a better \vspace between the rows of this array and I'd like to add a horizzontal dash line between 4th and 5th rows (but only for three first coloumns) and why the vertical line is broken? Thank you so much.

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6
  • How or where is \Scale defined? Commented Sep 4, 2021 at 17:06
  • Your code does not compile. Anyway, have you tried to change \arraystretch? Commented Sep 4, 2021 at 17:08
  • To get the extra vertical line segment, change \multicolumn{3}{c}{...} to \multicolumn{3}{c|}{...}. Commented Sep 4, 2021 at 17:12
  • @JuanCastano I don't know \arraystretch Commented Sep 4, 2021 at 17:16
  • Take a look at this post: tex.stackexchange.com/questions/564125/where-is-arraystretch. Commented Sep 4, 2021 at 17:18

4 Answers 4

Reset to default
4

Don't use \vspace to increase the separation between rows in an array. Instead, set \arraystretch to a number greater than 1. In the code below, I run \renewcommand\arraystretch{1.5}.

enter image description here

\documentclass{book}
\usepackage{mathtools} % for '\coloneqq' macro
\usepackage{stix}
\usepackage{multirow}
\newcommand{\Tonde}[1]{\left(#1\right)}
\newcommand*{\Scale}[2][4]{\scalebox{#1}{$#2$}}%

\begin{document}

\renewcommand\arraystretch{1.5} % <-- new

\begin{equation}\label{A_MEG_Blocchi}
A^{(\:\:)} \coloneqq
\Tonde{
  \begin{array}{c|c}
    \multicolumn{2}{c}{}\\
    \cline{2-2}
    \phantom{K} & K % <-- '\phantom{K}' is new
  \end{array}}
=
\Tonde{
  \begin{array}{ccc|ccc}
    a_{11}^{(1)}&\cdots&\cdots&\cdots&\cdots&a_{1n}^{(1)} \\
    0&\ddots&\ddots&\cdots&\cdots&\vdots \\
    \vdots&\ddots&a_{k-1,k-1}^{(k-1)}&\cdots&\cdots&a_{k-1,n}^{(k-1)} \\[1mm]
    \cline{4-6}
    \multicolumn{3}{c|}{\multirow{3}{*}{\Scale[4]{$0$}}}
    &a_{kk}^{(k)} & \cdots & a_{kn}^{(k)} \\
    & & & \vdots&\ddots&\vdots\\
    &&&a_{nk}^{(k)}&\cdots&a_{k+1,n}^{(k)}
  \end{array}}
\end{equation}

\end{document}
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2
  • Thank you @Mico. If I'd like to space only this array, how must I do? And then, the horizzontal dashed line? Thnak you again Commented Sep 4, 2021 at 20:33
  • @Puck - To limit the scope of the \renewcommand\arraystretch{1.5} directive to just this particular equation environment, place a \begingroup instruction right before \renewcommand\arraystretch{1.5} and an \endgroup instruction immediately after \end{equation}. I'm afraid I don't know what you're referring to with "the horizzontal dashed line". Please elaborate. Commented Sep 4, 2021 at 21:20
4

An alternative solution with tblr environment of the new LaTeX3 package tabularray:

\documentclass{book}
\usepackage{mathtools}
\usepackage{stix}

\newcommand{\Tonde}[1]{\left(#1\right)}

\newcommand*{\Scale}[2][4]{\scalebox{#1}{$#2$}}%
\newcommand*{\Resize}[2]{\resizebox{#1}{!}{$#2$}}%

\usepackage{tabularray}
\SetTblrInner{rowsep=4pt}

\begin{document}

\begin{equation}\label{A_MEG_Blocchi}
A^{(\:\:)} \coloneqq
\Tonde{
  \begin{tblr}{c|c}
    \SetCell[c=2]{c} & \\
    \cline{2-2}
    \phantom{K} & K % <-- '\phantom{K}' is new
  \end{tblr}}
=
\Tonde{
  \begin{tblr}{ccc|ccc}
    a_{11}^{(1)}&\cdots&\cdots&\cdots&\cdots&a_{1n}^{(1)} \\
    0&\ddots&\ddots&\cdots&\cdots&\vdots \\
    \vdots&\ddots&a_{k-1,k-1}^{(k-1)}&\cdots&\cdots&a_{k-1,n}^{(k-1)} \\
    \cline[dashed]{1-3}\cline{4-6}
    \SetCell[r=3,c=3]{c}\Scale[4]{$0$} & &
    &a_{kk}^{(k)} & \cdots & a_{kn}^{(k)} \\
    & & & \vdots&\ddots&\vdots\\
    &&&a_{nk}^{(k)}&\cdots&a_{k+1,n}^{(k)}
  \end{tblr}}
\end{equation}

\end{document}

enter image description here

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1
  • Thank you @LJR, never seen this tblr-environment. I think that your great solution will be useful for me in order to substitute other particular array-environment. Thank you so much again Commented Sep 5, 2021 at 7:46
2

Here is what I would do with {pNiceArray} of nicematrix.

\documentclass{book}
\usepackage{mathtools,stix}
\usepackage{nicematrix,tikz}

\begin{document}

\begin{equation}\label{A_MEG_Blocchi}
\renewcommand{\arraystretch}{1.6}
A^{(\:\:)} \coloneqq
\begin{pNiceMatrix}[margin=3pt,columns-width=5mm]
  \\
  & K 
\CodeAfter
  \tikz \draw (3-|2) |- (2-|3) ;
\end{pNiceMatrix}
=
\begin{pNiceMatrix}[margin=3pt,xdots/line-style=dotted,xdots/shorten=1pt]
  a_{11}^{(1)}&\Cdots&&&&a_{1n}^{(1)} \\
  0&\Ddots&&&&\Vdots \\
  0&0&a_{k-1,k-1}^{(k-1)}&&\Cdots&a_{k-1,n}^{(k-1)} \\
  \Block{3-3}<\Huge>{$0$} &  &  &a_{kk}^{(k)} & \Cdots & a_{kn}^{(k)} \\
  & & & \Vdots&\Ddots&\Vdots\\
  &&&a_{nk}^{(k)}&\Cdots&a_{k+1,n}^{(k)}
\CodeAfter
  \line{2-1}{3-1}
  \line{2-1}{3-2}
  \line{3-1}{3-2}
  \begin{tikzpicture}
    \draw (1-|4) -- (last-|4) (4-|4) -- (4-|last) ; 
    \draw [dashed] (4-|1) -- (4-|4) ;
  \end{tikzpicture}
\end{pNiceMatrix}
\end{equation}

\end{document}

You need several compilations (because nicematrix uses PGF/Tikz nodes under the hood).

Output of the above code

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1

I solved my problem so:

\begin{equation}\label{A_MEG_Blocchi}
A^{(\:\:)} \coloneqq
\Tonde{
  \begin{array}{c|c}
    \multicolumn{2}{c}{}\\
    \cline{2-2}
    \phantom{K} & K % <-- '\phantom{K}' is new
  \end{array}}
=
\Tonde{\begingroup{
  \begin{array}{ccc|ccc}
    a_{11}^{(1)}&\cdots&\cdots&\cdots&\cdots&a_{1n}^{(1)} \\
    0&\ddots&\ddots&\cdots&\cdots&\vdots \\
    \vdots&\ddots&a_{k-1,k-1}^{(k-1)}&\cdots&\cdots&a_{k-1,n}^{(k-1)} \\[1mm]
    \cline{4-6}
    0&\cdots&0&a_{kk}^{(k)} & \cdots & a_{kn}^{(k)} \\[-7.5mm] \hdotsfor[0.75]{3}\\[-2.5mm]
    \multicolumn{3}{c|}{\multirow{3}{*}{\Scale[4]{$0$}}}
    &\vdots&\ddots&\vdots\\
    &&&a_{nk}^{(k)}&\cdots&a_{k+1,n}^{(k)}
  \end{array}}\endgroup}
\end{equation}

Thank you Mico!

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