TikZ-PGF – How to Create a Footnote in Node in a TikZ Picture

Question

I would like to add a footnote to a node in a TikZ picture, but every solution I could imagine fails. I tried using a minipage, too.

\documentclass[a4paper,10pt]{scrartcl}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
\foreach \x/\y/\number/\year in {
  0.5/0.46/ 4.624/2001,
  1.5/0.89/ 8.965/2002\footnotemark,
  2.5/1.18/11.892/2003
}
{
  \draw (\x cm, 0 cm) rectangle (0.5 cm + \x cm, \y cm) node at (0.25 cm + \x cm, \y cm + 0.25 cm) {\tiny\number};
  \node[rotate=45, left] at (0.6 cm +\x cm,-0.1cm) {\year};
};
\end{tikzpicture}
\footnotetext{foo}
\end{document}

The output shown is

! Missing number, treated as zero.
<to be read again>
               }
l.18   }
    ;

The footnote text is displayed correctly, but the footnote mark is not.

I tried using a minipage as following. I replaced

\node[rotate=45, left] at (0.6 cm +\x cm,-0.1cm) {\year};

with

\node[rotate=45, left] at (0.6 cm +\x cm,-0.1cm) {\begin{minipage}{2em}\year\end{minipage}};

Follow-up question: How to create multiple footnotes with the hyperref package?

\documentclass[a4paper,10pt]{scrartcl}
\usepackage{tikz}

\usepackage[
pdfpagelabels,
pdfstartview=FitH,
plainpages=false,
hypertexnames=false
]{hyperref}

\begin{document}

\begin{tikzpicture}

  \foreach \x/\y/\Number/\Year in {
      0.5/0.46/ 4.624/2001,
      1.5/0.89/ 8.965/2002\footnotemark,
      2.5/1.18/11.892/2003\footnotemark
  }
  {
    \draw (\x cm, 0 cm) rectangle (0.5 cm + \x cm, \y cm) node at (0.25 cm + \x cm, \y cm + 0.25 cm) {\tiny\Number};
    \node[rotate=45, left] at (0.6 cm +\x cm,-0.1cm) {\Year};


  };

\end{tikzpicture}

\footnotetext{foo1}
\footnotetext{foo2}

\end{document}

Answer 1

It's quite dangerous using \number in that context, because it's an important primitive of TeX that's indeed used for printing the footnote number; that's why TeX gets very confused: it means something completely unexpected when it's necessary to use its original meaning.

Also \year is a primitive; better using another name also for it.

\documentclass[a4paper,10pt]{scrartcl}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
\foreach \x/\y/\Number/\Year in {
  0.5/0.46/ 4.624/2001,
  1.5/0.89/ 8.965/2002\footnotemark,
  2.5/1.18/11.892/2003
}
{
  \draw (\x cm, 0 cm) rectangle (0.5 cm + \x cm, \y cm)
        node at (0.25 cm + \x cm, \y cm + 0.25 cm) {\tiny\Number};
  \node[rotate=45, left] at (0.6 cm +\x cm,-0.1cm) {\Year};
};
\end{tikzpicture}
\footnotetext{foo}
\end{document}