Graphical connection between a matrix and a label

Question

I need to show the connection of an element of a matrix with a label, like this:

enter image description here

This is some code that I write:

\[
\mathrm{A^{(0)}}=
\quad
\left(
\begin{array}{cccc:c@{}}
    2 &  2 &  1 &  1 &  7 \\
    1 & -1 &  2 & -1 &  1 \\
    3 &  2 & -3 & -2 &  4 \\
    4 &  3 &  2 &  1 & 12 \\
\end{array}
\right)
%
\begin{array}{cccc}
           eq1 &  m21 & = & 1/2 \\
           eq2 &  m31 & = & 3/2 \\
           eq3 &  m41 & = & 2   \\
           eq4 &      &   &     \\
\end{array}
\]

So, how i can do this?

Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. I'm not sure I get what exactly do you want: the rectangle on the left, or the arrows in the middle? — yo', Sep 29 '14 at 18:42

Werner · Answer 1 · 2014-09-29T19:50:33.423

3

One option here would be to use a text right overlap:

enter image description here

\documentclass{article}
\usepackage{arydshln,amsmath}
\begin{document}

\[
  \mathrm{A^{(0)}} =
  \left[\hspace{.5\arraycolsep}
  \begin{array}{rrrr:r}
    2 &  2 &  1 &  1 &  7 \rlap{\quad\small$\rightarrow$ eq1} \\
    \cline{1-1}
    \multicolumn{1}{|r|}{1} & -1 &  2 & -1 &  1 \rlap{\quad\small$\rightarrow$ eq2} \\
    \multicolumn{1}{|r|}{3} &  2 & -3 & -2 &  4 \rlap{\quad\small$\rightarrow$ eq3} \\
    \multicolumn{1}{|r|}{4} &  3 &  2 &  1 & 12 \rlap{\quad\small$\rightarrow$ eq4} \\
    \cline{1-1}
  \end{array}
  \right]
  \qquad\qquad
  \left\{
  \renewcommand{\arraystretch}{1.4}
  \begin{array}{l}
    m_{21} = \tfrac{1}{2} \\
    m_{31} = \tfrac{3}{2} \\
    m_{41} = 2
  \end{array}
  \right.
\]

\end{document}

You can, of course, adjust the spacing \quad to suit your needs.

edited Sep 29 '14 at 19:50

answered Sep 29 '14 at 18:57

Werner

603,163

thanks, but how can I put the square around the first column? I tried using Tikz, but the result was not good. – João Gerd Zell de Mattos Sep 29 '14 at 19:09
@JoãoGerdZelldeMattos: Updated. Also see Highlight elements in the matrix. – Werner Sep 29 '14 at 19:35
@Werner: you forgot there should be indices next to the m's. – Bernard Sep 29 '14 at 19:44
@Bernard: They do look like indices now. Thanks. – Werner Sep 29 '14 at 19:50

wipet · Answer 2 · 2014-09-29T20:30:19.420

Let me show, how to solve this task from plain TeX point of view. But these macros work in LaTeX too. And without any packages.

\def\|{\quad \lower4pt\vbox to13.2pt{%
   \cleaders\vbox{\hrule height2.2pt width.4pt\kern2.2pt}\vfil}}
\def\bt{\rlap{\kern-3pt\vbox to0pt{\kern-10pt\hrule\hbox{\vrule height39pt\quad\vrule}\hrule}}}
\def\eq#1{\rlap{\quad\ $\to$ eq#1}}
\def\rmatrix#1{\vcenter{\offinterlineskip\halign{&\enspace\hfil$##$\enspace\cr #1\crcr}}}
\def\crs{\cr\noalign{\kern5pt}}
\def\A{{\rm A}}

$$
\A^{(0)} = \left(\,\rmatrix{
    2 &   2 &   1 &   1 \|&  7 \eq1 \cr
\bt 1 &  -1 &   2 &  -1 \|&  1 \eq2 \cr
    3 &   2 &  -3 &  -2 \|&  4 \eq3 \cr
    4 &   3 &   2 &   1 \|& 12 \eq4 \cr
}\right)\qquad\qquad\
\cases{m21={1\over2}\crs m31={3\over2}\crs m41=2}
$$

\bye

matrix

Graphical connection between a matrix and a label

2 Answers2