Math & Science ⇒ Bmatrix Column Headings

[statsbob]

I'm a stats professor, and I often show matrices in which columns represent variables. Sometimes I wish to include the variable names as headers on top of the columns. I have just been putting them as the first row of the matrix, but that's not as clear in terms of the brackets and matrix dimensions. Here is a simple example:

Code: Select all

\begin{bmatrix}
  \mu & \tau_1 & \tau_2 \\
  1 & 1 & 0 \\
  1 & 1 & 0 \\
  1 & 1 & 0 \\
  1 & 0 & 1 \\
  1 & 0 & 1 \\
  1 & 0 & 1
\end{bmatrix}

Can I create this so the headings line up with the columns of the matrix, but are outside of the brackets? Thanks!!

Bob

[localghost]

Take a look at the \bordermatrix described in the "Math mode" document (Section 5 - Matrix, p. 20f).


Best regards and welcome to the board
Thorsten

[Stefan Kottwitz]

Hi Bob,

welcome to the board!
You could nest arrays, like

Code: Select all

\[
\begin{array}{c}
\begin{matrix}
\mu & \!\tau_1\! & \tau_2
\end{matrix} \\
\left[\ \begin{matrix}
1 & 1 & 0 \\
1 & 1 & 0 \\
1 & 1 & 0 \\
1 & 0 & 1 \\
1 & 0 & 1 \\
1 & 0 & 1
\end{matrix}\ \right]
\end{array}
\]

I've just used the matrix environment inside \left[ ... \right] to get more space after the brackets.

Stefan

[statsbob]

Thanks for the quick responses, I really appreciate it. I've just been learning on my own since I decided this spring to start preparing my notes in Latex. I'm constantly learning.

I will have to look into the bordermatrix environment later this week. That looks great, but I'm not yet familiar with macros in Latex and am not sure how to use that yet.

The problem I would encounter with second suggestion is that the headings aren't strictly aligned with the matrix columns. I believe I must have the headings in the same environment.
e.g.
\[
\begin{array}{c}
\begin{matrix}
\mu & (\beta\tau)_1 & \tau_2
\end{matrix} \\
\left[\ \begin{matrix}
1 & 1 & 0 \\
1 & 1 & 0 \\
1 & 1 & 0 \\
1 & 0 & 1 \\
1 & 0 & 1 \\
1 & 0 & 1
\end{matrix}\ \right]
\end{array}
\]

Bob

[localghost]

At first, please use the code environment for posting longer pieces of source code to keep a post clear.

I will have to look into the bordermatrix environment later this week. That looks great, but I'm not yet familiar with macros in Latex and am not sure how to use that yet.

According to the examples in the linked document you can easily get what you want.

Code: Select all

\documentclass[11pt,a4paper,english]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}

\makeatletter
\newif\if@borderstar
\def\bordermatrix{\@ifnextchar*{%
\@borderstartrue\@bordermatrix@i}{\@borderstarfalse\@bordermatrix@i*}%
}
\def\@bordermatrix@i*{\@ifnextchar[{\@bordermatrix@ii}{\@bordermatrix@ii[()]}}
\def\@bordermatrix@ii[#1]#2{%
\begingroup
\m@th\@tempdima8.75\p@\setbox\z@\vbox{%
\def\cr{\crcr\noalign{\kern 2\p@\global\let\cr\endline }}%
\ialign {$##$\hfil\kern 2\p@\kern\@tempdima & \thinspace %
\hfil $##$\hfil && \quad\hfil $##$\hfil\crcr\omit\strut %
\hfil\crcr\noalign{\kern -\baselineskip}#2\crcr\omit %
\strut\cr}}%
\setbox\tw@\vbox{\unvcopy\z@\global\setbox\@ne\lastbox}%
\setbox\tw@\hbox{\unhbox\@ne\unskip\global\setbox\@ne\lastbox}%
\setbox\tw@\hbox{%
$\kern\wd\@ne\kern -\@tempdima\left\@firstoftwo#1%
\if@borderstar\kern2pt\else\kern -\wd\@ne\fi%
\global\setbox\@ne\vbox{\box\@ne\if@borderstar\else\kern 2\p@\fi}%
\vcenter{\if@borderstar\else\kern -\ht\@ne\fi%
\unvbox\z@\kern-\if@borderstar2\fi\baselineskip}%
\if@borderstar\kern-2\@tempdima\kern2\p@\else\,\fi\right\@secondoftwo#1 $%
}\null \;\vbox{\kern\ht\@ne\box\tw@}%
\endgroup
}
\makeatother

\begin{document}
  \[
    \bordermatrix[{[]}]{%
      & \mu & \tau_1 & \tau_2 \cr
      & 1 & 1 & 0 \cr
      & 1 & 1 & 0 \cr
      & 1 & 1 & 0 \cr
      & 1 & 0 & 1 \cr
      & 1 & 0 & 1 \cr
      & 1 & 0 & 1
    }
  \]
\end{document}

[Stefan Kottwitz]

Adjustments could be made like

Code: Select all

\documentclass[a4paper,10pt]{article}
\usepackage{amsmath}
\usepackage{mathtools}
\begin{document}
\[
\begin{array}{c}
\begin{matrix}
\mu & \mathclap{\tau_1} & \tau_2
\end{matrix} \\
\begin{bmatrix}
1 & 1 & 0 \\
1 & 1 & 0 \\
1 & 1 & 0 \\
1 & 0 & 1 \\
1 & 0 & 1 \\
1 & 0 & 1
\end{bmatrix}
\end{array}
\]
\end{document}

or a package like bigdelim could be used, or big delimiters and nested arrays.

Stefan

[statsbob]

Again thanks for both of your responses. The result of the bordermatrix script looks good. Is it reasonable to say that that code is something that one would usually save to a file to be inputted in the preamble when needed?

[localghost]

[...] Is it reasonable to say that that code is something that one would usually save to a file to be inputted in the preamble when needed?

The final decision is up to you.