separate style and content in table

Question

I am generating tables from a program and its a bit inconvenient that I have to intersperse style and content information. For example, in the following note how \cellcolor{red} is interspersed among the data. It would be easier to generate if there could be a statement or statements at point %% A or at point %% B in the code below that indicated that in column 3, rows 3-4 that the cells should be colored red. Is this achievable?

\documentclass{article}
\usepackage{colortbl}
\usepackage[table]{xcolor}
\usepackage{tabu}
\begin{document}

\begin{center}
%% A
\begin{tabu}{XXXX}
%% B
1 & 2 & 3 & 4 \\
5 & 6 & 7 & 8 \\
9 & 10 & \cellcolor{red} 11 & 12 \\
13 & 14 & \cellcolor{red} 15 & 16 \\
17 & 18 & 19 & 20 \\
\end{tabu}
\end{center}

\end{document}

Output:

By the way, I have already seen this question which is also about separating style and content but as far as I understand it does not really provide the type of solution to the example shown above requested here.

EDIT: In case its not clear here is the type of code that would be desirable:

\documentclass{article}
\usepackage{colortbl}
\usepackage[table]{xcolor}
\usepackage{tabu}
\begin{document}

\begin{center}
\begin{tabu}{XXXX}
\preCell{3}{3}{\cellcolor{red}} % specifies that row 3 col 3 is red
\preCell{4}{3}{\cellcolor{red}} % specifies that row 4 col 3 is red
1 & 2 & 3 & 4 \\
5 & 6 & 7 & 8 \\
9 & 10 & 11 & 12 \\
13 & 14 & 15 & 16 \\
17 & 18 & 19 & 20 \\
\end{tabu}
\end{center}

\end{document}

Answer 1

1. All Cells:

If you want all the cells in a particular column to have the same formatting, you can use the collcell package which allows you to pass the entry of each column to a command for further processing:

Alternatively, you could also use the array package, and define:

\newcolumntype{R}{>{\cellcolor{red}}X<{}}

2. Select Cells:

If you only want a select number of cells to be colored then you can use additional commands such as \ActivateColorCell to enable cell coloring and \DectivateColorCell to disable the cell coloring as desired:

Notes:

• I used the etoolbox package to provide the toggle to test if coloring is enabled, but it should be easy to adapt this to not require that package if desired using solutions from LaTeX conditional expression.

---

Code: collcell (all cells):

\documentclass{article}
\usepackage{collcell}
\usepackage{colortbl}
\usepackage[table]{xcolor}
\usepackage{tabu}

\newcommand{\ColorCellRed}[1]{\cellcolor{red}{#1}}

\newcolumntype{R}{>{\collectcell\ColorCellRed}X<{\endcollectcell}}


\begin{document}

\begin{center}
\begin{tabu}{XXRX}
   1 &  2 &  3 &  4 \\
   5 &  6 &  7 &  8 \\
   9 & 10 & 11 & 12 \\
  13 & 14 & 15 & 16 \\
  17 & 18 & 19 & 20 \\
\end{tabu}
\end{center}

\end{document}

---

Code: array (all cells):

\documentclass{article}
\usepackage{array}
\usepackage{colortbl}
\usepackage[table]{xcolor}
\usepackage{tabu}

\newcolumntype{R}{>{\cellcolor{red}}X<{}}


\begin{document}

\begin{center}
\begin{tabu}{XXRX}
   1 &  2 &  3 &  4 \\
   5 &  6 &  7 &  8 \\
   9 & 10 & 11 & 12 \\
  13 & 14 & 15 & 16 \\
  17 & 18 & 19 & 20 \\
\end{tabu}
\end{center}

\end{document}

Code: collcell (some cells):

\documentclass{article}
\usepackage{collcell}
\usepackage{colortbl}
\usepackage[table]{xcolor}
\usepackage{tabu}
\usepackage{etoolbox}

\newtoggle{EnableColorCell}
\togglefalse{EnableColorCell}

\newcommand*{\ActivateColorCell}{\global\toggletrue{EnableColorCell}}
\newcommand*{\DectivateColorCell}{\global\togglefalse{EnableColorCell}}
\newcommand{\ColorCellRed}[1]{%
    \iftoggle{EnableColorCell}{%
        \cellcolor{red}{#1}%
    }{%
        #1% no cell color as it is disabled
    }%
}

\newcolumntype{R}{>{\collectcell\ColorCellRed}X<{\endcollectcell}}


\begin{document}
\begin{center}
\begin{tabu}{XXRX}
   1 &  2 &  3 &  4 \\
   5 &  6 &  7 &  8 \\\ActivateColorCell
   9 & 10 & 11 & 12 \\
  13 & 14 & 15 & 16 \\\DectivateColorCell
  17 & 18 & 19 & 20 \\
\end{tabu}
\end{center}
\end{document}

Code: array (some cells):

\documentclass{article}
\usepackage{array}
\usepackage{colortbl}
\usepackage[table]{xcolor}
\usepackage{tabu}
\usepackage{etoolbox}

\newtoggle{EnableColorCell}
\togglefalse{EnableColorCell}
\newcommand*{\ActivateColorCell}{\global\toggletrue{EnableColorCell}}
\newcommand*{\DectivateColorCell}{\global\togglefalse{EnableColorCell}}


\newcolumntype{R}{>{\iftoggle{EnableColorCell}{\cellcolor{red}}{}}X<{}}


\begin{document}

\begin{center}
\begin{tabu}{XXRX}
   1 &  2 &  3 &  4 \\
   5 &  6 &  7 &  8 \\\ActivateColorCell
   9 & 10 & 11 & 12 \\
  13 & 14 & 15 & 16 \\\DectivateColorCell
  17 & 18 & 19 & 20 \\
\end{tabu}
\end{center}

\end{document}

Answer 2

You can do something like this, but it will probably break as soon as \multicolum is involved:

\documentclass{article}
\usepackage{colortbl}
\usepackage[table]{xcolor}
\usepackage{tabu}
\begin{document}
\makeatletter
\newcommand\preCell[3]{\@namedef{tabstyle-#1-#2}{#3}}
\makeatother
\newcounter{rowcounter}
\newcounter{columncounter}

\begin{center}
\setcounter{rowcounter}{0}
\setcounter{columncounter}{0}

\preCell{3}{3}{\cellcolor{red}} % specifies that row 3 col 3 is red
\preCell{4}{3}{\cellcolor{red}} % specifies that row 4 col 3 is red

\begin{tabu}{>{\stepcounter{rowcounter}%
               \setcounter{columncounter}{0}\stepcounter{columncounter}%
               \csname tabstyle-\therowcounter-\thecolumncounter\endcsname}X
             >{\stepcounter{columncounter}%
              \csname tabstyle-\therowcounter-\thecolumncounter\endcsname}X
             >{\stepcounter{columncounter}%
              \csname tabstyle-\therowcounter-\thecolumncounter\endcsname}X
             >{\stepcounter{columncounter}%
              \csname tabstyle-\therowcounter-\thecolumncounter\endcsname}X}
1 & 2 & 3 & 4 \\
5 & 6 & 7 & 8 \\
9 & 10 & 11 & 12 \\
13 & 14 & 15 & 16 \\
17 & 18 & 19 & 20 \\
\end{tabu}
\end{center}

\end{document}