A macro for looping through a pgfplotstable set by cell

Question

Hi following on from the following question on multi-line headers with pgfplotstable, the solution was to set each affected cell individually. I decided to throw together a command to do that but keep hitting an the error Argument of \reserved@a has an extra }. <inserted text> \par

The snippet I'm using is attached below -

\DeclareRobustCommand{\pgfplotstableeach}[4][1]{
    \foreach \col in {#1,...,#2}
        \foreach \ro in {0,...,#3}
        {\ifthenelse{\col=#2 \AND \ro=#3}{every row \ro\  column \col/.style=\{#4\}}{every row \ro\  column \col/.style=\{#4\},}}   
}

and this works fine to produce the text outside a pgfplotstabletypeset environment but fails inside one.

I've tried \newcommand and \newcommand{\protect\pgfplotstableeach}{<macro>} but neither works.

If I replace the macro with the text I want to input e.g. "every row 0 column 1/.style=..." it fails with a Missing \endcsname inserted. <to be read again> \protect. I actually thought this would be fairly straightforward but I'm completely bewildered by the error.

What am I doing wrong?

edited to include MWE below

\documentclass{article}
\usepackage{array,datatool,pgfplotstable}

    \begin{filecontents}{sample.csv}
       item,2008,2009,2010,2011
           ,Actual,Actual,Forecast,Forecast
           ,GBP,GBP,GBP,GBP
           ,('000),('000),('000),('000) rounded
       Area 1 OP, 1000000,1500000,1750000,250000
       Area 2 OP, 400000,500000, 450000,-50000
       Area 51 OP, 300000,375000,390000,15000
       No P, 1250000, 1000000, 950000, 50000
       Residuals, 800000, 80000, 90000, 10000
  \end{filecontents}

  \DeclareRobustCommand{\pgfplotstableeach}[4][1]{
       \foreach \col in {#1,...,#2}
          \foreach \ro in {0,...,#3}
           {\ifthenelse{\col=#2 \AND \ro=#3}
                       {every row \ro\  column \col/.style=\{#4\}}
                       {every row \ro\  column \col/.style=\{#4\},}}   
  }

\begin{document}

\pgfplotstableread[col sep=comma,header=false]{sample.csv}\mystuff

\pgfplotstabletypeset[fixed,
\pgfplotstableeach{4}{4}{string type}]\mystuff

\end{document}

Answer 1

Your example relies on illegal assumptions on how expansion works in TeX/PGF. In your particular case, it suffers from two problems:

1. \foreach looses everything which has been set inside of it unless you explicitly declare it as global. In your case, it looses every option.

2. You cannot execute custom macros directly inside of option lists.

A solution for (1.) would be to collect all your options into one huge (global!) list and execute it after the \foreach statements.

A solution for (2.) is to set all these options before \pgfplotstabletypeset. You could surround the complete statements with curly braces: this would delimit the effect (just as inside of \foreach).

Interestingly, the solution for (1.) is much more involved than it sounds. This is because the expansion of TeX is different from almost anything else that you might have encountered.

Here is a solution. You may want to decide if you want to learn the details of expansion control (i.e. questions like "what is \toks*?" or "what is \expandafter?") by studying http://pgfplots.sourceforge.net/TeX-programming-notes.pdf

\documentclass{article}
\usepackage{array,datatool,pgfplotstable}

    \begin{filecontents}{sample.csv}
       item,2008,2009,2010,2011
           ,Actual,Actual,Forecast,Forecast
           ,GBP,GBP,GBP,GBP
           ,('000),('000),('000),('000) rounded
       Area 1 OP, 1000000,1500000,1750000,250000
       Area 2 OP, 400000,500000, 450000,-50000
       Area 51 OP, 300000,375000,390000,15000
       No P, 1250000, 1000000, 950000, 50000
       Residuals, 800000, 80000, 90000, 10000
  \end{filecontents}

  \newcommand{\pgfplotstableeach}[4][1]{
    \xdef\ACCUM{}%
       \foreach \col in {#1,...,#2} {%
          \foreach \ro in {0,...,#3}
           {%
            \toks0=\expandafter{\ACCUM}%
            \edef\temp{every row \ro\space column \col/.style}%
            \toks1={#4}%
            \xdef\ACCUM{\the\toks0 \temp={\the\toks1},}%
           }%
         }%
    \message{setting \meaning\ACCUM^^J}%
     \expandafter\pgfplotstableset\expandafter{\ACCUM},
  }

\begin{document}

\pgfplotstableread[col sep=comma,header=false]{sample.csv}\mystuff

\pgfplotstableeach{4}{4}{string type}
\pgfplotstabletypeset[fixed,]\mystuff

\end{document}

note that the example is incomplete; it results in compilation failures (because only selected cells have string type).