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I want a symbol written above each coordinate, which is taken from a table with a "label" column.

At first I wanted to just use \node[above] at (axis cs:\x, \y){\Label} but this causes a not obvious error, most likely related to the \Label expansion. The command \addplot+ coordinates {(\x, \y)} node[above] {Something}; with the text of the node Something works, but as soon as I put inside the node a command that is defined from a table element, I get a non-obvious error.

! Undefined control sequence. \pgfplotsretval -> node[above] {\Label } l.39

At the same time, \addplot understands the coordinates macro...

% !TeX program = pdflatex % !TeX encoding = utf8 \documentclass{standalone} \usepackage{pgfplots} \usepackage{pgfplotstable} \begin{document} \pgfplotstableread{ x y label 4 0.511 e 5 2.2 u 6 4.7 d 7 96 s 8 105.7 mu 9 1270 c 10 1777 tau 11 4180 b 12 173000 t }\loadedtable \begin{tikzpicture} \begin{semilogyaxis} \foreach \row in {0,...,8} { \pgfplotstablegetelem{\row}{x}\of\loadedtable \let\x=\pgfplotsretval \pgfplotstablegetelem{\row}{y}\of\loadedtable \let\y=\pgfplotsretval \pgfplotstablegetelem{\row}{label}\of\loadedtable \let\Label=\pgfplotsretval \addplot+ coordinates {(\x, \y)} node[above] {\Label}; } \end{semilogyaxis} \end{tikzpicture} \end{document}
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  • Why do you think you need a loop? Commented Mar 15 at 19:17
  • Data may appear or disappear in the table Commented Mar 15 at 19:17

2 Answers 2

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There is no problem with \let. But \foreach stores the \node instruction as is, and when the picture is delivered at \end{tikzpicture}, what you get as coordinates is (\x,\y) for each one of them, but \x and \y have no longer a meaning.

Solution: \expanded.

\foreach \row in {0,1,...,8} { \pgfplotstablegetelem{\row}{x}\of\loadedtable \let\x\pgfplotsretval \pgfplotstablegetelem{\row}{y}\of\loadedtable \let\y\pgfplotsretval \pgfplotstablegetelem{\row}{label}\of\loadedtable \let\Label\pgfplotsretval \expanded{\noexpand\node[above] at (\x, \y) {$\Label$};} }

output

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The answer turned out to be a compilation of already known solutions. The tikz macros inside \foreach need to wrapped in \edef\temp{\noexpand ...}\temp tags.

% !TeX program = pdflatex % !TeX encoding = utf8 \documentclass{standalone} \usepackage{pgfplots} \pgfplotsset{compat=1.18} \usepackage{pgfplotstable} \begin{document} \pgfplotstableread{ x y label 4 0.511 e 5 2.2 u 6 4.7 d 7 96 s 8 105.7 mu 9 1270 c 10 1777 tau 11 4180 b 12 173000 t }\loadedtable \begin{tikzpicture} \begin{semilogyaxis} \addplot table[x=x, y=y] \loadedtable; \foreach \row in {0,1,...,8} { \pgfplotstablegetelem{\row}{x}\of\loadedtable \edef\x{\pgfplotsretval} \pgfplotstablegetelem{\row}{y}\of\loadedtable \edef\y{\pgfplotsretval} \pgfplotstablegetelem{\row}{label}\of\loadedtable \edef\Label{\pgfplotsretval} \edef\temp{ \noexpand\node[above] at (\x, \y) {$\Label$}; } \temp } \end{semilogyaxis} \end{tikzpicture} \end{document}
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  • 2
    The fact that \let works is surprising... probably due to some expansion magic. Much better if you use \edef\x{\pgfplotsretval} and so on. And you do not need axis cs: if you add the (suggested by the package) \pgfplotsset{compat=1.18} Commented Mar 15 at 19:33
  • 1
    @Rmano Yes, thank you. I took that into account Commented Mar 15 at 19:41

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