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I studied the examples in Highlight elements in the matrix and developed my example:

enter image description here

The code is the following:

 \documentclass{article} \usepackage{tikz} \usetikzlibrary{matrix} \begin{document} \begin{tikzpicture} \matrix (m)[matrix of math nodes,nodes in empty cells, ] { 0 & -26 & 111 & 5 & -1 & 2 \\ 2666 & 67 & 55 & 77 & 6 & -1 \\ -1 & 3 & 3 & 3 & 3 & 8 \\ 1 & 2 & 5 & 77 & 7 & 1 \\ 1 & 33 & 44 & 66 & 998888 & -266 \\ -2 & 1 & 7 & -1 & 2 & 80 \\ } ; \draw (m-1-1.north west) -- (m-2-1.south west) -- (m-2-2.south east) -- (m-1-2.north east) -- cycle; \end{tikzpicture} \end{document}

What I do not like is that the box is skew.

Another feature that I do not like is that the column widths are not equal - the width of the column containing 998888 is larger.

Is it possible to control these aspects?

I would like to stick to tikz because it has an attractive feature - being able to draw a dotted line across multiple columns/rows (not addressed in the above example).

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4 Answers 4

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The rectangle of the example can be easily drawn by specifying opposite corners:

\draw (m-2-1.south west) rectangle (m-1-2.north east);

The general case is covered by Ignasi's answer.

The nodes can be set with a minimum width of the largest entry:

minimum width=width("998888")

Full example:

\documentclass{article} \usepackage{tikz} \usetikzlibrary{matrix} \begin{document} \begin{tikzpicture} \matrix (m)[ matrix of math nodes, nodes in empty cells, minimum width=width("998888"), ] { 0 & -26 & 111 & 5 & -1 & 2 \\ 2666 & 67 & 55 & 77 & 6 & -1 \\ -1 & 3 & 3 & 3 & 3 & 8 \\ 1 & 2 & 5 & 77 & 7 & 1 \\ 1 & 33 & 44 & 66 & 998888 & -266 \\ -2 & 1 & 7 & -1 & 2 & 80 \\ } ; \draw (m-2-1.south west) rectangle (m-1-2.north east); \end{tikzpicture} \end{document}

Result

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It's important to understand that a TikZ-matrix only aligns inner nodes but it doesn't change nodes' size. It's esay to understand if you draw all nodes:

enter image description here

As you can see every node has its own size, being them into a matrix only distribute them in rows and columns. So the command 

\draw (m-1-1.north west) -- (m-2-1.south west) -- (m-2-2.south east) -- (m-1-2.north east) -- cycle;

will produce a skewed rectangle.

If you don't want to modify your code the easiest solution could be:

\draw (m-1-1.north-|m-1-2.west) rectangle (m-2-1.east|-m-2-2.south);

You can also force all nodes to have same width with an option like text width={width(998888)} which can be accompained by align=right and all nodes will be verticaly aligned to the right in every column.

nodes={text width={width(998888)}, align=right}

With this option you could use draw (m-1-1.north west) rectangle (m-2-2.south east) to define the desired region.

The coplete code is:

 \documentclass{article} \usepackage{tikz} \usetikzlibrary{matrix} \begin{document} \begin{tikzpicture} \matrix (m)[matrix of math nodes, nodes in empty cells, nodes={text width={width(998888)}, align=right} ] { 0 & -26 & 111 & 5 & -1 & 2 \\ 2666 & 67 & 55 & 77 & 6 & -1 \\ -1 & 3 & 3 & 3 & 3 & 8 \\ 1 & 2 & 5 & 77 & 7 & 1 \\ 1 & 33 & 44 & 66 & 998888 & -266 \\ -2 & 1 & 7 & -1 & 2 & 80 \\ } ; \draw (m-1-1.north-|m-2-1.west) rectangle (m-2-2.east|-m-2-2.south); \end{tikzpicture} \end{document}

And the result:

enter image description here

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It's rather easy with pstricks: use an ordinary bmatrix enclosed in a postscript environment, put two empty nodes A and B at the relevant places, and join them with an \ncbox command with the convenient size parameters. A second solution (more of an automatic solution) consists in drawing a \psframe which joins two diagonally opposed nodes:

\documentclass[12pt, svgnames]{article} \usepackage{mathtools, nccmath} \usepackage{pst-node} \usepackage{auto-pst-pdf} \begin{document} \begin{equation*} \begin{postscript} \begin{bmatrix} 0 & -26\pnode{C} & 111 & 5 & -1 & 2 \\ \:\pnode[-0.05,0]{A} 2666 & 67\pnode[0.25, 0]{B} & 55 & 77 & 6 & -1 \\ -1 & 3 & 3 & 3 & 3 & 8 \\ 1 & 2 & 5 & 77 & 7 & 1 \\ 1 & 33 & 44 & 66 & \medmath{998888} & -266 \\ -2 & 1 & 7 & -1 & 2 & 80 \end{bmatrix} \ncbox[boxheight=0.85, boxdepth=0.1, linecolor=IndianRed]{A}{B} \end{postscript} \end{equation*} \smallskip \begin{equation*} \psset{linearc =0.2,linejoin=1} \begin{postscript} \begin{bmatrix} 0 &-26\: \pnode[0,0.35]{C} & 111 & 5 & -1 & 2 \\ \,\pnode[0,-0.1]{A}\:2666 & 67 & 55 & 77 & 6 & -1 \\ -1 & 3 & 3 & 3 & 3 & 8 \\ 1 & 2 & 5 & 77 & 7 & 1 \\ 1 & 33 & 44 & 66 & \medmath{998888} & -266 \\ -2 & 1 & 7 & -1 & 2 & 80 \end{bmatrix} \psframe[linecolor=IndianRed](A)(C) \end{postscript} \end{equation*} \end{document}

enter image description here

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  • Is there a solution that provides an automatic height of the box? Doing that manually seems to me a little bit archaic with Latex. Commented Oct 7, 2016 at 2:19
  • @pzorba75: Yes, more or less. As you can see, I used only two nodes (that's what \ncbox is done for), whereas we have to enclose 4 values in a frame. We also can use two nodes, in positions (2,1) and (1,2). What can't be fully automated is the vertical offset of these nodes. Please see my updated answer. Commented Oct 7, 2016 at 8:37
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With {bNiceMatrix} of nicematrix, which, as the Tikz library matrix does, create a PGF/Tikz node under each of the matrix (if you need them...).

\documentclass{article} \usepackage{nicematrix} \begin{document} $\begin{bNiceMatrix}[r,left-margin=0.6em] \Block[draw]{2-3}{} 0 & -26 & 111 & 5 & -1 & 2 \\ 2666 & 67 & 55 & 77 & 6 & -1 \\ -1 & 3 & 3 & 3 & 3 & 8 \\ 1 & 2 & 5 & 77 & 7 & 1 \\ 1 & 33 & 44 & 66 & 998888 & -266 \\ -2 & 1 & 7 & -1 & 2 & 80 \\ \end{bNiceMatrix}$ \end{document}

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

Output of the above code

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