Settting PGFplots axis environment options by means of \newcommand and {\newlength,\setlength}

Question

Because I often use the same options for multiple axes in my LaTeX documents, I use the following code to simplify my life.

\documentclass{article}
\usepackage{pgfplots}
\newcommand{\linecolora}{blue}
\newcommand{\marka}{o}
\newcommand{\plotoptsa}{color=\linecolora,mark=\marka}
\newcommand{\xlabela}{Test test 123}
\newlength\figurewidth
\setlength{\figurewidth}{\columnwidth}
\newcommand{\axisoptsa}{width=100,xlabel=\xlabela}
\newcommand{\axisoptsb}{ymin=-8,ymax=-3}
\begin{document}
    \begin{tikzpicture}
        \begin{axis}[\axisoptsa,\axisoptsb]
            \expandafter\addplot\expandafter[\plotoptsa] coordinates
                {
                    (2,-2.8559703)
                    (3,-3.5301677)
                    (4,-4.3050655)
                    (5,-5.1413136)
                    (6,-6.0322865)
                    (7,-6.9675052)
                    (8,-7.9377747)
                };
         \end{axis}     
    \end{tikzpicture}
\end{document}

It works like a charm! However, if I change width=100 into the defined width=\figurewidth, I get Missing \endcsname inserted. error. Using

\expandafter\begin{axis}\expandafter[\axisoptsa,\axisoptsb]

does not help.

Answer 1

You shouldn't do stuff like that with newcommands, rather define your own styles. This makes it possible to override them. Defining styles ensures, that the diagrams you are producing all have the same look and style.

Instead of having everything as flexible as you have it, I would suggest one style per type of diagram.

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.9}
\newlength\figurewidth
\setlength{\figurewidth}{\columnwidth}
\newcommand{\marka}{o}
%You can define colors like this:
\colorlet{linecolora}{blue}
%and define new styles like this:
\pgfplotsset{
    xlabela/.style={Test test 123},
    axisA/.style={width=\figurewidth,xlabel={xlabela}},
    axisB/.style={ymin=-8,ymax=-3},
    plotoptsa/.style={color=linecolora,mark=\marka}
}

\begin{document}
\begin{tikzpicture}
    \begin{axis}[axisA,axisB,xlabel={manually and conscious override of style}]
        \addplot [plotoptsa]
        coordinates
        {
            (2,-2.8559703)
            (3,-3.5301677)
            (4,-4.3050655)
            (5,-5.1413136)
            (6,-6.0322865)
            (7,-6.9675052)
            (8,-7.9377747)
        };
    \end{axis}     
\end{tikzpicture}
\end{document}