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I have tried repeatedly to google for the solution to this problem. I have a matrix that looks like this. enter image description here

But I want it to look like this. enter image description here

Notice how the B, C, D and E are "very tightly centered" around the A. Here is my code.

\documentclass[12pt,a4paper]{article} \usepackage{amsmath} \begin{document} \newcommand{\matt}[5] { $ \begin{bmatrix} \begin{array}{ c c c } \begin{bmatrix} 2+r & -1 \\ -1 & 2+r & -1 \\ & \ddots & \ddots & \ddots \\ & & \ddots & \ddots & \ddots \\ & & & -1 & 2+r & -1 \\ & & & & -1 & 2+r \\ \end{bmatrix} & {#3} & \\ {#4} & {#1} & {#2} \\ & {#5} & \begin{bmatrix} 2+r & -1 \\ -1 & 2+r & -1 \\ & \ddots & \ddots & \ddots \\ & & \ddots & \ddots & \ddots \\ & & & -1 & 2+r & -1 \\ & & & & -1 & 2+r \\ \end{bmatrix} \\ \end{array} \end{bmatrix} $ } \matt {A} {B} {C} {D} {E} \end{document}

Any thoughts?

Thanks, Bob.

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  • Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. Nice question indeed! However, (with my mathematics typesetter hat on) I don't think you hould do that if $C$, $D$, $B$ and $F$ are matrices or vectors and not numbers. Commented Apr 6, 2015 at 21:30
  • Ah .. but for my need, they are just C, D, etc. Sometimes I need Z_n or Z_{n+1} .. but that's it. Commented Apr 6, 2015 at 21:38

2 Answers 2

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Use adjustbox to get the right vertical alignment:

\documentclass[12pt,a4paper]{article} \usepackage{amsmath,adjustbox} \newenvironment{Pbmatrix}[1][c] {\begin{adjustbox}{valign=#1}$\begin{bmatrix}} {\end{bmatrix}$\end{adjustbox}} \newcommand{\matt}[5]{ \begin{bmatrix} \begin{Pbmatrix}[b] 2+r & -1 \\ -1 & 2+r & -1 \\ & \ddots & \ddots & \ddots \\ & & \ddots & \ddots & \ddots \\ & & & -1 & 2+r & -1 \\ & & & & -1 & 2+r \\ \end{Pbmatrix} & #3 \\ \hfill #4 & #1 & #2\hfill \\ & #5 & \begin{Pbmatrix}[t] 2+r & -1 \\ -1 & 2+r & -1 \\ & \ddots & \ddots & \ddots \\ & & \ddots & \ddots & \ddots \\ & & & -1 & 2+r & -1 \\ & & & & -1 & 2+r \\ \end{Pbmatrix} \end{bmatrix} } \begin{document} \[ \matt {A} {B} {C} {D} {E} \] \end{document}

The auxiliary Pbmatrix environment has an alignment optional argument to get top or bottom alignment.

enter image description here

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  • Could you show me how to resize the entire matrix so that it is 90% of its size? It is now too wide for my page. Commented Apr 7, 2015 at 1:11
  • @BobZigon You can always do \scalebox{.9}{$\matt{A}{B}{C}{D}{E}$} (with the graphicx package), but I probably would give a symbolic name to the matrix in the corners. Commented Apr 7, 2015 at 9:49
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For information, here is what you can do with nicematrix.

\documentclass[12pt,a4paper]{article} \usepackage{nicematrix} \begin{document} \begin{equation*} \setlength{\arraycolsep}{4pt} \left[\begin{array}{@{}rcl@{}} \begin{bNiceMatrix}[b] 2+r & -1 \\ -1 & 2+r & -1 \\ & \Ddots & \Ddots & \Ddots \\ & & \Ddots & \Ddots & \Ddots \\ & & & -1 & 2+r & -1 \\ & & & & -1 & 2+r \\ \end{bNiceMatrix} & C \\ D & A & B \\ & E & \begin{bNiceMatrix}[t] 2+r & -1 \\ -1 & 2+r & -1 \\ & \Ddots & \Ddots & \Ddots \\ & & \Ddots & \Ddots & \Ddots \\ & & & -1 & 2+r & -1 \\ & & & & -1 & 2+r \\ \end{bNiceMatrix} \end{array}\right] \end{equation*} \end{document}

You need several compilations (because nicematrix uses PGF/Tikz nodes under the hood).

Output of the above code

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