Subdividing a matrix

Question

\documentclass[12pt,a4paper]{article}
%------------------------------------------------------------
\usepackage{amsmath,amssymb,amsthm}
\begin{document}
\[ \begin{pmatrix}
1 &2 &0&\cdots& 0\\
3& 4 &0&\cdots& 0\\
0 & 0 &0&\cdots& 0\\
\vdots & \vdots & \vdots & \vdots\\
0 & 0 &0&\cdots& 0\\
\end{pmatrix}\]
and
\[U_k= \begin{bmatrix}
J_{k\times k} &0_{k\times (n-k)} \\
0_{(n-k)\times k}& I_{(n-k)\times (n-k)}\\
\end{bmatrix}\]
\end{document}

I want to subdivise the following two matrices

Like the following one

You can use also nicematrix package. – Sebastiano Mar 25 '20 at 17:49 — Sebastiano, Mar 25 '20 at 17:49

score 4 · Answer 1 · edited Mar 25 '20 at 22:23

4

https://tex.stackexchange.com/a/240865/197451

\documentclass{article}
\begin{document}
  \[
    M = \left(
    \begin{array}{c|c}
      A & B\\
      \hline
      C & D
    \end{array}
    \right)
  \]
\end{document}

for bigger matrices

Source clicking on this word.

edited Mar 25 '20 at 22:23

Sebastiano

54,118

answered Mar 25 '20 at 15:37

js bibra

21,280

Please for the first matrix how can I do?Thank you – Schüler Mar 25 '20 at 15:40
Your second link is dead. – Zarko Mar 25 '20 at 16:21
https://wp.kntu.ac.ir/hadizadeh/pdf/latex/lesson_12[1].pdf -- and -- https://wp.kntu.ac.ir/ftorabi/onlinecourses.html – js bibra Mar 25 '20 at 16:29
1

@Zarko Resurrected the lost link ahahah. – Sebastiano Mar 25 '20 at 22:24

Zarko · Accepted Answer · 2020-03-25T16:38:36.103

A short resume of @js bibra (very long answer) answer:

\documentclass[12pt,a4paper]{article}

\begin{document}
    \[ 
\left[\begin{array}{cc|*{3}{c}}
1       & 2      & 0      & \cdots & 0      \\
3       & 4      & 0      & \cdots & 0      \\
    \hline
0       & 0      & 0      & \cdots & 0      \\
\vdots  & \vdots & \vdots & \ddots & \vdots \\
0       & 0      & 0      & \cdots & 0      
\end{array}\right]
\]
and
\[
U_k = \left[\begin{array}{c|c}
    J_{k\times k}       & 0_{k\times (n-k)}     \\
        \hline
    0_{(n-k)\times k}   & I_{(n-k)\times (n-k)}
      \end{array}\right]
\]
\end{document}

No resume but....Exhumed :-) ahahah – Sebastiano Mar 25 '20 at 22:25 — Sebastiano, Mar 25 '20 at 22:25

score 3 · Answer 3 · answered Mar 25 '20 at 16:22

Simple with pstricks: insert empty nodes at the relevant places in the matrix, and connect them with lines:

\documentclass[12pt, a4paper, svgnames]{article}
%------------------------------------------------------------
\usepackage{amsmath,amssymb,amsthm}
\usepackage{pst-node}

\begin{document}

\[ \begin{pmatrix}
1 &2 \pnode[1ex, 1.6ex]{V}&0&\cdots& 0\\
\pnode[-0.6ex, -0.7ex]{H}3& 4 &0&\cdots& 0\pnode[0.6ex, -0.7ex]{K}\\
0 & 0 &0&\cdots& 0\\
\vdots & \vdots & \vdots & \vdots\\
0 & 0 \pnode[1ex, -0.5ex]{W} &0&\cdots& 0
\end{pmatrix}
\psset{linecolor=IndianRed}
\ncline{V}{W}\ncline{H}{K}\]
and
\[U_k= \begin{bmatrix}
J_{k\times k} &\pnode[0,1.6ex] {V}& 0_{k\times (n-k)} \\
\pnode[-0.3ex,1.9ex]{H} 0_{(n-k)\times k}&\pnode[0,-0.6ex] {W} & I_{(n-k)\times (n-k)}\pnode[0.3ex, 1.9ex]{K}
\end{bmatrix}
\psset{linecolor=SteelBlue}
\ncline{V}{W}\ncline{H}{K} \]

\end{document}

Subdividing a matrix

3 Answers3

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