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I'm using pgfplotstable to create standalone graphs of test data. I've included pgffor and I'm trying to use a \foreach loop to iterate over the three output channels for a given unit under test within a single groupplot. Lucky for me, I'm getting compilation errors that refer to the index variable (called \chan), and which point to lines outside the loop, where \chan isn't used.

Here's a stripped-down version of my file that's causing trouble:

\documentclass[tikz]{standalone}
\usepackage{pgfplotstable}
\usepackage{pgffor}
\usepackage{siunitx}
\usepgfplotslibrary{groupplots}
\pgfplotsset{compat=1.18}

\newcommand{\voltticks}{-10,0,...,30}
\newcommand{\voltmin}{-18}
\newcommand{\voltmax}{35}
\newcommand{\currmin}{-0.5}
\newcommand{\currmax}{8}


% Different color for each channel on each unit
\newcommand{\uutchan}[2]{%
    \ifcase #1 error% There's no uut #0
        \or \ifcase #2 colorerror% nor any channel #0
            \or black%
            \or brown%
            \or red%
        \fi%
        \or \ifcase #2 colorerror%
            \or orange%
            \or yellow%
            \or green%
        \fi%
        \or \ifcase #2 colorerror%
            \or blue%
            \or purple%
            \or grey%
        \fi%
    \fi}


\pgfplotsset{every axis/.append style={
            xmin=0,
            xmax=5,
            xtick={1,2,...,5},
            }}


\newcommand{\uut}{1}


% All the data files have the same filename structure
\newcommand{\lvdata}[1]{plot-data/lv-data-uut-\uut-ch-#1.csv}


\begin{document}
\begin{tikzpicture}[>=stealth]
    \begin{groupplot}[
        group style={
            group size=1 by 2,
        },
        no markers,
        width=6in,
    ]
        \nextgroupplot[
            ymin=\voltmin,
            ymax=\voltmax,
            ytick=\voltticks,
            ylabel={Voltage (\si{\volt})},
            xticklabels=\empty,
            title={Boy, I wish this would work right},
            height=1.75in,
        ]
            \foreach \chan in {1,2,3}{%
                \addplot[\uutchan{\uut}{\chan}] table [%
                    col sep=comma,%
                    x={elapsed_time},%
                    y={voltage},%
                ] {\lvdata{\chan}};%
                \addlegendentry{Channel \chan}%
            }                                   % <<-- end of the \foreach loop


    \nextgroupplot[
        ymin=\currmin,
        ymax=\currmax,
        xlabel={Elapsed Time},
        ylabel={Current (\si{\ampere})},
        height=1.75in,
    ]                                       % &lt;&lt;-- here's line 79
        \addplot[\uutchan{\uut}{1}] table [
            col sep=comma,
            x={elapsed_time},
            y={current},
        ] {\lvdata{1}};
        \addlegendentry{Channel 1}
        \addplot[\uutchan{\uut}{2}] table [
            col sep=comma,
            x={elapsed_time},
            y={current},
        ] {\lvdata{2}};
        \addlegendentry{Channel 2}
        \addplot[\uutchan{\uut}{3}] table [
            col sep=comma,
            x={elapsed_time},
            y={current},
        ] {\lvdata{3}};
        \addlegendentry{Channel 3}

\end{groupplot}





\end{tikzpicture}
\end{document}

Here's the error message I get:

(/usr/local/texlive/2021/texmf-dist/tex/latex/translations/translations-basic-d
ictionary-english.trsl)
! Undefined control sequence.
<argument> \chan

l.79            ]

I don't understand why it looks like \chan is being called several lines after the end of the loop.

I know that run-on commands sometimes show up a little later in the file, but I've double-checked my brace count to make sure I didn't forget to close the code block, and it's correct.

Also worth noting is that if I don't use the \foreach loop, there are no problems. The way the second groupplot is written shows what that would look like.

What am I doing wrong?

Edit: Updated with a M(non-)WE instead of a code snippet.

Contents of plot-data/lv-data-uut-1-ch-1.csv:

elapsed_time,voltage,current
1,5.12088502740541,1.18375845641884
2,5.81177332147156,1.6640415277584
3,6.3936508576718,2.47855204713269
4,5.77677606311296,1.88676641772499
5,6.08716354605412,2.68562189308305

Contents of plot-data/lv-data-uut-1-ch-2.csv:

elapsed_time,voltage,current
1,14.7367967957342,3.58490117433496
2,14.2603519819053,3.15772195035904
3,15.219470298334,2.60505323186182
4,15.8054999682348,4.0885748772842
5,14.602837758358,3.92571012858714

Contents of plot-data/lv-data-uut-1-ch-3.csv:

elapsed_time,voltage,current
1,-4.68980292044475,6.07093702142046
2,-5.52369547515492,6.60095794734899
3,-3.14599831983585,6.49047991092652
4,-5.57765267954762,6.86674835669737
5,-4.3030082035212,5.32605451112347
Gern Blanston
  • 161

0 Answers0