[Tex/LaTex] Horizontal line representing row vector in matrix

math-modematrices

I would like to produce a graphical representation of a matrix as stack of row vectors. Because I will be publishing the math on a website, I have access to the amsmath package but no others. I find that I can produce a representation of a matrix as a stack of column vectors using the following code

\left(
\begin{array}{ccc} 
\vline & \vline & \vline \\
\vline & \vline & \vline \\
\vline & \vline & \vline \\
\end{array}
\right)

What I would like is a transpose of this.

This question is similar to How do I typeset vertical and horizontal lines inside a matrix? and Long dashes for denoting omitted columns of a matrix, but when I apply the approaches found in those posts, I do not obtain a continuous horizontal line.

Best Answer

Saying simply \vline is not the best method, in my opinion. Try

\documentclass{article}
\usepackage{amsmath}

\begin{document}
$\begin{pmatrix}
\kern.6em\vline & \kern.2em\vline\kern.2em & \vline\kern.6em \\
\kern.6em\vline & \kern.2em\vline\kern.2em & \vline\kern.6em \\
\kern.6em\vline & \kern.2em\vline\kern.2em & \vline\kern.6em \\
\end{pmatrix}
\begin{pmatrix}
\rule[.5ex]{3.5em}{0.4pt}\\
\rule[.5ex]{3.5em}{0.4pt}\\
\rule[.5ex]{3.5em}{0.4pt}
\end{pmatrix}$
\end{document}

enter image description here

Related Solutions

[Tex/LaTex] Horizontal row separation line in tikz matrix (like \hline in tabular)

You can use a style that uses execute at end cell to draw a horizontal line at the top or bottom edge of selected cells. By applying this style to complete using row <number>/.style, you can get an effect similar to \hline:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix}
\begin{document}

\tikzset{toprule/.style={%
        execute at end cell={%
            \draw [line cap=rect,#1] (\tikzmatrixname-\the\pgfmatrixcurrentrow-\the\pgfmatrixcurrentcolumn.north west) -- (\tikzmatrixname-\the\pgfmatrixcurrentrow-\the\pgfmatrixcurrentcolumn.north east);%
        }
    },
    bottomrule/.style={%
        execute at end cell={%
            \draw [line cap=rect,#1] (\tikzmatrixname-\the\pgfmatrixcurrentrow-\the\pgfmatrixcurrentcolumn.south west) -- (\tikzmatrixname-\the\pgfmatrixcurrentrow-\the\pgfmatrixcurrentcolumn.south east);%
        }
    }
}

\begin{tikzpicture}
\matrix [matrix of nodes,
    row sep=-\pgflinewidth,
    column sep=-\pgflinewidth,
    nodes={rectangle,minimum width=3em,outer sep=0pt},
    row 1/.style={toprule=thick,bottomrule},
    row 3/.style={bottomrule=thick}]
{
0   & 6 & 5\\
1   & 3 & 7\\
21 & 22 & 23\\
};
\end{tikzpicture}
\end{document}

matrix of cells with horizontal lines

[Tex/LaTex] Typesetting a Row Vector

You have to collect the row beforehand, as doing it inside an array environment is quite difficult, as TeX ends a cell as soon as it sees an &. I prefer to do in with a token register and the \count255 scratch counter.

We collect two arguments: the first is the number of entries, the second the first entry, in order to initialize the token register with it. We set the counter to the number of requested element (since we have already collected one, we step it down immediately).

Then we start the recursion; the macro \rowvectnexta examines the value of the counter; if it's still greater than 0, it calls \rowvecnextb that gathers another argument, stores it into the token register (adding an &) and steps down the counter; otherwise it builds the pmatrix by releasing the contents of the register.

\newtoks\rowvectoks
\newcommand{\rowvec}[2]{%
  \rowvectoks={#2}\count255=#1\relax
  \advance\count255 by -1
  \rowvecnexta}
\newcommand{\rowvecnexta}{%
  \ifnum\count255>0
    \expandafter\rowvecnextb
  \else
    \begin{pmatrix}\the\rowvectoks\end{pmatrix}
  \fi}
\newcommand\rowvecnextb[1]{%
    \rowvectoks=\expandafter{\the\rowvectoks&#1}%
    \advance\count255 by -1
    \rowvecnexta}

It shouldn't be a big limitation the fact that you need at least one element:

\rowvec{1}{a}
\rowvec{2}{a}{b}
\rowvec{3}{a}{b}{c}

Notice: \usepackage{amsmath} is required. So a minimal example might be the following.

\documentclass{article}
\usepackage{amsmath}

\newtoks\rowvectoks
\newcommand{\rowvec}[2]{%
  \rowvectoks={#2}\count255=#1\relax
  \advance\count255 by -1
  \rowvecnexta}
\newcommand{\rowvecnexta}{%
  \ifnum\count255>0
    \expandafter\rowvecnextb
  \else
    \begin{pmatrix}\the\rowvectoks\end{pmatrix}
  \fi}
\newcommand\rowvecnextb[1]{%
    \rowvectoks=\expandafter{\the\rowvectoks&#1}%
    \advance\count255 by -1
    \rowvecnexta}

\begin{document}

$\rowvec{1}{a}$
$\rowvec{2}{a}{b}$
$\rowvec{3}{a}{b}{c}$

\end{document}

A completely different solution that can be generalized to column vectors uses xparse and LaTeX3.

\documentclass{article}
\usepackage{amsmath}
\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand{\Rowvec}{ O{,} m }
 {
  \vector_main:nnnn { p } { & } { #1 } { #2 }
 }
\NewDocumentCommand{\Colvec}{ O{,} m }
 {
  \vector_main:nnnn { p } { \\ } { #1 } { #2 }
 }

\seq_new:N \l__vector_arg_seq
\cs_new_protected:Npn \vector_main:nnnn #1 #2 #3 #4
 {
  \seq_set_split:Nnn \l__vector_arg_seq { #3 } { #4 }
  \begin{#1matrix}
  \seq_use:Nnnn \l__vector_arg_seq { #2 } { #2 } { #2 }
  \end{#1matrix}
 }
\ExplSyntaxOff

\begin{document}

$\Rowvec{a}\Rowvec{a,b}\Rowvec[;]{a;b;c}$

$\Colvec{a}\Colvec{a,b}\Colvec[;]{a;b;c}$

\end{document}

The optional argument is the delimiter to be used to separate entries in the list given as argument.

It's sufficient to change { p } into { b } in the two main definitions to get brackets instead of parentheses.

enter image description here

Note: this requires expl3 dated September 2012 or later.

Best Answer

Related Solutions

[Tex/LaTex] Horizontal row separation line in tikz matrix (like \hline in tabular)

[Tex/LaTex] Typesetting a Row Vector

Related Question