Macro to outline a cell in pgfplotstable

Question

Still struggling with the \expandafter and \noexpand tex macros.

I'm trying to put a table together using pgfplotstable.

In this case the code is something like

\documentclass{article}
\usepackage{pgfplotstable}

\def\outline{\noexpand\fbox{{##1}}}

\begin{document}
\pgfplotstableread[row sep=\\,col sep=&,header=false]{%
1 & 2 & 3 & 4\\%
5 & 6 & 7 & 8\\%
9 & 10 & 11 & 12\\%
}\mytable

\pgfplotstabletypeset[
debug,
column name={},
every row 2 column 1/.style={postproc cell content/.style={@cell content=\outline}}
]\mytable

\end{document}

and gives the error you can't use macro parameter character in horizontal restricted mode. I f I escape the ##1 it replaces cell contents with ##1.

What I'm trying to do is eventually have a line that says something like:

every row 2 column 1/.style=\outline and a macro along the lines of

\def\outline{%
\{postproc cell content.style=%
\{@cell content=\noexpand\fbox{##1}\}\}}

What am I doing wrong?

Answer 1

You are on the wrong track: the problem is unrelated to expansion control.

The problem is that your invocation of \outline does not communicate the argument - and the definition of \outline has no argument defined, although it requires one.

Once you fix these two points, you can come back to escaping #1 by ##1.

This here appears to work as desired:

\documentclass{article}
\usepackage{pgfplotstable}

\def\outline#1{\fbox{{#1}}}

\begin{document}
\pgfplotstableread[row sep=\\,col sep=&,header=false]{%
1 & 2 & 3 & 4\\%
5 & 6 & 7 & 8\\%
9 & 10 & 11 & 12\\%
}\mytable

\pgfplotstabletypeset[
debug,
column name={},
every row 2 column 1/.style={postproc cell content/.style={@cell content=\outline{##1}}}
]\mytable

\end{document}

I changed the definition of \outline (\def requires you to list the expected arguments in the definition) and the invocation of \outline. Note that the latter really requires ##1 (because #1 is the argument to every row 2 column 1 in that context and you want the argument to postproc cell content).

---

EDIT:

concerning the second part of your question and your comment on this answer: yes, it might be possible to define a style by means of a macro which expands to key-value assignments. But it is clearly not a best-practice. In fact, if it works, it might be luck.

If you want to have some sort of style which says "outline this cell", then you might be better of with something of sorts

% preamble:
\pgfplotstableset{
   outline/.style={postproc cell content/.style={@cell content=\outline{##1}}}
}

%code:
\pgfplotstabletypeset[
debug,
column name={},
every row 2 column 1/.style={outline},
]\mytable