How to circle multiple cells? (special case)

Question

I need to circle multiple cells, on different rows/columns. This is a problem which has been solved.

However, I have a more particular case of the problem. I need to draw a circle that needs to illustrate that the elements of the last row are together with the ones of the first row, resulting in a matrix like in the example.

Here is the way I have implemented the table:

\begin{tabular}{c c|c|c|c|c|}
    \multirow{7}{*}{\parbox{1.5cm}{$DataQ_2$}}
    & \multicolumn{5}{c}{$Q_1Q_0$} \\
    \cline{3-6}
    \multicolumn{2}{c|}{} & 00 & 01 & 11 & 10 \\ 
    \cline{2-6}
    & \multicolumn{1}{|c|}{00} & X & 1 & 1 & 1 \\
    \cline{2-6}
    & \multicolumn{1}{|c|}{01} & 0 & 1 & 1 & 0 \\
    \cline{2-6}
    & \multicolumn{1}{|c|}{11} & 1 & 1 & 1 & 1 \\
    \cline{2-6}
    & \multicolumn{1}{|c|}{10} & X & 1 & 1 & 0 \\
    \cline{2-6}
\end{tabular}

This is the way it looks:

This is how I want it to look(sorry for the shitty drawing quality... I hope it's obvious that I want though):

PS If you tell me a more elegant way to implement the table to look like this, it would be appreciated.

Answer 1

One option is to use the tikzmark library (from TikZ) to place some marks and then to use those marks to draw the frames; one possibility (adjust the settings according to your needs):

The code:

\documentclass{article}
\usepackage{multirow}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{tikzmark}

\begin{document}

\[
\renewcommand\arraystretch{1.2}
\begin{array}{c|c|c|c|c|c|}
    \multicolumn{1}{c}{}\multirow{7}{*}{$\text{Data}Q_2$}
     & \multicolumn{5}{c}{Q_1Q_0} \\
    \cline{3-6}
    \multicolumn{1}{c}{} & & 00 & 01 & 11 & 10 \\ 
    \cline{2-6}
    & 00 & \tikzmark{startup}X & 1 & 1 & 1\tikzmark{endup} \\
    \cline{2-6}
    & 01 & 0 & 1 & 1 & 0 \\
    \cline{2-6}
    & 11 & 1 & 1 & 1 & 1 \\
    \cline{2-6}
    & 10 & \tikzmark{startdown}X & 1 & 1 & 0\tikzmark{enddown} \\
    \cline{2-6}
\end{array}
\]

\begin{tikzpicture}[remember picture,overlay]
\foreach \Val in {up,down}
{
\draw[rounded corners,red,thick]
  ([shift={(-0.5\tabcolsep,-0.5ex)}]pic cs:start\Val) 
    rectangle 
  ([shift={(0.5\tabcolsep,2ex)}]pic cs:end\Val);
}
\end{tikzpicture}

\end{document}

If the boxes should have one end open:

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{tikzmark}

\begin{document}

\[
\renewcommand\arraystretch{1.2}
\text{Data}Q_2\begin{array}{c|c|c|c|c|c|}
    \multicolumn{1}{c}{}
     & \multicolumn{5}{c}{Q_1Q_0} \\
    \cline{3-6}
    \multicolumn{1}{c}{} & & 00 & 01 & 11 & 10 \\ 
    \cline{2-6}
    & 00 & \tikzmark{startup}X & 1 & 1 & 1\tikzmark{endup} \\
    \cline{2-6}
    & 01 & 0 & 1 & 1 & 0 \\
    \cline{2-6}
    & 11 & 1 & 1 & 1 & 1 \\
    \cline{2-6}
    & 10 & \tikzmark{startdown}X & 1 & 1 & 0\tikzmark{enddown} \\
    \cline{2-6}
\end{array}
\]

\begin{tikzpicture}[remember picture,overlay]
\draw[rounded corners,red,thick]
  ([shift={(-0.5\tabcolsep,2ex)}]pic cs:startup) -- 
  ++(0,-2.6ex) -- 
  ([shift={(0.5\tabcolsep,-0.6ex)}]pic cs:endup) --
  ++(0,2.6ex);
\draw[rounded corners,red,thick]
  ([shift={(-0.5\tabcolsep,-0.8ex)}]pic cs:startdown) -- 
  ++(0,2.8ex) -- 
  ([shift={(0.5\tabcolsep,2ex)}]pic cs:enddown) --
  ++(0,-2.8ex);
\end{tikzpicture}

\end{document}

Remarks:

• Since some internal calculations are involved, the code needs two runs to stabilize.

• Since the content of the table is mostly maths, I change to array instead of tabular.

• I used

  \renewcommand\arraystretch{1.2}
  

  to have some more "air" around the cell content.

• In the second example code I suppressed the \multirow and simply placed \text{Data}Q_2 next to the array.