How to use a loop for labels on line graphs in pgfplots

Question

I want to do a graph like below. Showing the duration of an intervention in a country.

generated by this code:

\begin{tikzpicture}
\begin{axis}[
    date coordinates in=x,
    xticklabel={\day/\month},
    xticklabel style={rotate=90,anchor=near xticklabel},
    axis y line=none,
    axis x line=bottom,
    xmin = 2020-01-25
    ]
\addplot +[color=black,no marks,ultra thick]
table[x=date,y=HUN] {tables/policies_time.txt} node[left,pos=0] {HUN};
\addplot +[color=black,no marks,ultra thick]
table[x=date,y=DEU] {tables/policies_time.txt} node[left,pos=0] {DEU};
\addplot +[color=black,no marks,ultra thick]
table[x=date,y=AUT] {tables/policies_time.txt} node[left,pos=0] {AUT};
\end{axis}
\end{tikzpicture}

I want to use a for loop, because I have a much bigger set of countries. Therefor I make a loop and replace the labels "HUN", "DEU" and "AUT" by the running variable \isos in both the table[] part and the labeling node part. But this time the labels give an error, and do not appear.

Here is my code for the looped version:

\begin{tikzpicture}
\begin{axis}[
        date coordinates in=x,
        xticklabel={\day/\month},
        xticklabel style={rotate=90,anchor=near xticklabel},
        axis y line=none,
        axis x line=bottom,
        xmin = 2020-01-25
        ]
\makeatletter
\@for\isos:=HUN,DEU,AUT\do{
    \addplot +[color=black,no marks,ultra thick] table[x=date,y=\isos]    {tables/policies_time.txt}
    node[left,pos=0] {\isos};
    }
\makeatother
\end{axis}
\end{tikzpicture}

Do you have any suggestions, how to solve this problem?

Thank you,

Oliver

Answer 1

As this answer suggests, you will get into expansion trouble if you combine \foreach (or \@for) with \addplot in such a way. However, you can use \pgfplotsinvokeforeach for this:

\documentclass[border=2mm]{standalone}

\usepackage{pgfplots}
\pgfplotsset{compat=1.17}
\usepgfplotslibrary{dateplot}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
    date coordinates in=x,
    xticklabel={\day/\month},
    xticklabel style={rotate=90,anchor=near xticklabel},
    axis y line=none,
    axis x line=bottom,
    xmin = 2020-01-25
    ]
    \pgfplotsinvokeforeach{HUN,DEU,AUT}{
       \addplot +[color=black,no marks,ultra thick]
        table[x=date,y=#1] {tables/policies_time.txt} node[left,pos=0] {#1};
    }
\end{axis}
\end{tikzpicture}

\end{document}

As you did not provide any data to feed this graph, I cannot really test this.