How do I typeset vertical and horizontal lines inside a matrix?

Question

(From the notation used in course notes for Stanford CS229 available online.) I'm trying to typeset the following matrices made up of row or column vectors:

enter image description here

Any ideas?

Related: https://tex.stackexchange.com/questions/444807/matrix-and-vertical-lines-in-columns — EthanAlvaree, Mar 23 '23 at 20:58

score 26 · Accepted Answer · edited Sep 17 '15 at 01:06

26

You can use rules to create the vertical and horizontal bars and then just put them into your array directy.

\documentclass{article}
\usepackage{array}
\begin{document}
\newcommand*{\vertbar}{\rule[-1ex]{0.5pt}{2.5ex}}
\newcommand*{\horzbar}{\rule[.5ex]{2.5ex}{0.5pt}}

\[
A = 
\left[
  \begin{array}{cccc}
    \vertbar & \vertbar &        & \vertbar \\
    a_{1}    & a_{2}    & \ldots & a_{n}    \\
    \vertbar & \vertbar &        & \vertbar 
  \end{array}
\right]
\]
\setlength{\extrarowheight}{1ex}
\[
A =
\left[
  \begin{array}{ccc}
    \horzbar & a^{T}_{1} & \horzbar \\
    \horzbar & a^{T}_{2} & \horzbar \\
             & \vdots    &          \\
    \horzbar & a^{T}_{n} & \horzbar
  \end{array}
\right]
\]

\end{document}

result of code

edited Sep 17 '15 at 01:06

Travis Bemrose

429

answered Mar 08 '11 at 04:09

Alan Munn

218,180

If I use the exact code from above the vertical lines are not set correctly. Has anything changed? – Adam Aug 13 '14 at 13:04
No, the code still does exactly this for me. – Alan Munn Aug 13 '14 at 14:00
I also copied your exact code into a new document in TeXStudio, and the vertical spacing in the first matrix is wonky. See this image. – Travis Bemrose Sep 16 '15 at 20:01
@TravisBemrose Hmm, it seems there was a typo in the original code. I've changed the [1ex] to [-1ex]. But Herbert's \vrule works nicely too. – Alan Munn Sep 17 '15 at 00:28
Yep, once I clean up the \ newlines and remove some extra ampersands that showed up, it works great now. I'd been using \vert. – Travis Bemrose Sep 17 '15 at 00:36
(Fixed the formatting in the answer.) – Travis Bemrose Sep 17 '15 at 00:41

score 5 · Answer 2 · edited Jun 09 '17 at 15:58

5

\documentclass{article}
\usepackage{array}
\begin{document}

\[
A = 
\left[
  \begin{array}{cccc}
    \vrule & \vrule & & \vrule\\
    a_{1} & a_{2} & \ldots & a_{n} \\
    \vrule & \vrule & & \vrule 
  \end{array}
\right]
\]
\setlength{\extrarowheight}{1ex}
\[
A =
\left[
  \begin{tabular}{c>{$}c<{$}c}
    --- & a^{T}_{1} & ---\\
    --- & a^{T}_{2} & ---\\
    & \vdots & \\
    --- & a^{T}_{n} & ---
  \end{tabular}
\right]
\]

\end{document}

enter image description here

edited Jun 09 '17 at 15:58

Moriambar

11,466

answered Mar 08 '11 at 06:46

2

When I used --- in math mode, I got three minuses. I had to use \text{---} to make it work. But it seems to be working for you... any ideas why? – zellyn Mar 08 '11 at 19:16
no, in math it is always ---. I used a tabular which is by default in textmode ... – Mar 08 '11 at 19:20

score 3 · Answer 3 · answered Apr 20 '15 at 07:16

3

I like the following easy solution for vertical lines.

V = \begin{pmatrix}
\mid & \mid & & \mid \\
{\bf v}_{1} & {\bf v}_{2} & \cdots & {\bf v}_{r}\\
\mid & \mid & & \mid \\
\end{pmatrix}

answered Apr 20 '15 at 07:16

Luke Oeding

221

1

See Does it matter if I use \textit or \it, \bfseries or \bf, etc. and Will two-letter font style commands (\bf, \it, …) ever be resurrected in LaTeX? – Werner Sep 17 '15 at 00:33
I think the question in Werner's comment isn't relevant to the question at hand. Perhaps it belongs as its own question? – Luke Oeding Sep 18 '15 at 16:23
While it might not be relevant to this question per se, it's relevant in general, as \bf (and others) are deprecated in their usage. – Werner Sep 18 '15 at 16:25
Perhaps I should have used something like \vec{v} or \mathbf{v}. It's an easy modification. – Luke Oeding Sep 18 '15 at 16:53

How do I typeset vertical and horizontal lines inside a matrix?

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