6

I'd like to typeset a bunch of small 3x3 matrices to describe generators of certain ideals, as in this paper, p7.

enter image description here

Using smallmatrix works beautifully as long as I only want circles and bullets, but when I try to use multirow to merge cells and put a square across four entries of the matrix, it simply doesn't work. It works in the standard matrix or array environments, but they're far too large for what I need.

I've also tried How to model {smallmatrix} with {array}? but the squares get shrunk and it doesn't quite look right. Since I don't really understand the code in that thread, I don't know how to edit it to make it do what I want. I think it would be fine if I could make the squares a bit bigger.

Here is the code that hopefully illustrates what I'm trying to do. The smallarray environment comes directly from the thread I linked to above.

\documentclass{article} \usepackage{amssymb} \usepackage{amsmath} \usepackage{multirow} \newcommand{\ZZ}{\multicolumn{2}{c}{\multirow{2}{*}{$\square$}}} \newenvironment{smallarray}[1] {\null\,\vcenter\bgroup\scriptsize \renewcommand{\arraystretch}{0.7}% \arraycolsep=.13885em \hbox\bgroup$\array{@{}#1@{}}} {\endarray$\egroup\egroup\,\null} \begin{document} When there's no cells to merge, both smallmatrix (left) and smallarray (right) work fine. \begin{equation} \begin{smallmatrix} \circ & \circ & \bullet \\ \circ & \circ &\bullet \\ \circ & \circ & \circ \end{smallmatrix} \qquad \begin{smallarray}{ccc} \circ & \circ & \bullet \\ \circ & \circ &\bullet \\ \circ & \circ & \circ \end{smallarray} \end{equation} But when we try to merge some cells... \begin{equation} \begin{smallmatrix} \circ & \ZZ \\ \circ & & \\ \circ & \circ & \circ \end{smallmatrix} \qquad \begin{smallarray}{ccc} \circ & \ZZ \\ \circ & & \\ \circ & \circ & \circ \end{smallarray} \end{equation} ...smallmatrix just doesn't work. The second one is almost right and I'd happily just use that, but I also need a matrix of this form: \[\begin{smallarray}{ccc} \circ & \ZZ \\ \ZZ &\\ & & \circ \end{smallarray} \] and that's really not quite right. \end{document}

Any hints or suggestions would be appreciated.

Improve this question
1
  • 1
    Welcome to TeX.SX! \multirow can't work in smallmatrix. Commented Jul 19, 2013 at 11:33

1 Answer 1

Reset to default
4

One option using TikZ and a matrix of math nodes:

\documentclass{article} \usepackage{amssymb} \usepackage{amsmath} \usepackage{tikz} \usetikzlibrary{matrix,calc} \newenvironment{smallarray}[1] {\gdef\MatName{#1}\begin{tikzpicture} \matrix[ matrix of math nodes, row sep=-\pgflinewidth, column sep=-\pgflinewidth, nodes={inner sep=1pt,rectangle,text width=2mm,align=center}, text depth=0mm, text height=2mm, nodes in empty cells ] (#1)} {\end{tikzpicture}} \def\MyZ(#1,#2){% \draw ([xshift=-3.6pt,yshift=3.6pt] $ (\MatName-#1-#2)!0.5!(\MatName-\the\numexpr#1+1\relax-\the\numexpr#2+1\relax) $ ) rectangle ([xshift=3.6pt,yshift=-3.6pt] $ (\MatName-#1-#2)!0.5!(\MatName-\the\numexpr#1+1\relax-\the\numexpr#2+1\relax) $ ); } \begin{document} \begin{smallarray}{mat1} { \circ & \circ & \circ \\ \circ & \circ & \circ \\ \circ & \circ & \circ \\ }; \end{smallarray} \begin{smallarray}{mat2} { \circ & \circ & \bullet \\ \circ & \circ & \bullet \\ \circ & \circ & \circ \\ }; \end{smallarray} \begin{smallarray}{mat3} { \circ & & \\ \circ & & \\ \circ & \circ & \circ \\ }; \MyZ(1,2) \end{smallarray} \begin{smallarray}{mat4} { \circ & & \\ & & \\ & & \circ \\ }; \MyZ(1,2) \MyZ(2,1) \end{smallarray} \end{document}

enter image description here

The smallarray environment has one mandatory argument that will be used as the name of the matrix; the second matrix in the image was produced with:

\begin{smallarray}{mat2} { \circ & \circ & \bullet \\ \circ & \circ & \bullet \\ \circ & \circ & \circ \\ }; \end{smallarray}

\MyZ allows to draw the squares; the syntax is

\MyZ(x,y)

where x,y is the entry of the upper left corner of the square.

Improve this answer
2
  • That's lovely, thank you! For the matrix with two squares, I'm aiming to have just the corners of the square touching in the middle, but I guess that can be achieved by just tweaking the distances slightly? Commented Jul 19, 2013 at 13:54
  • @eithil You're welcome! Yes, you can change the lengths used in the shifts in the definition of \MyZ according to your needs; I changed them in my updated answer to produce the described result. Commented Jul 19, 2013 at 14:00

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.