# pgfplots - Placing Nodes on x Coordinates of a Plot

I want to plot some graphs in pgfplots and want to place nodes on the exact same x coordinate of the plot. The position of the note has to be set in x direction but free in y direction. Here is one example of the way it shouldn't be.

\documentclass{article}
\usepackage{pgfplots}

\begin{document}

\begin{figure}
\begin{tikzpicture}
\begin{axis}
\addplot {-x}  [yshift=8pt] node[pos=0.1] {$0,1$};
\addplot {x^2} [yshift=8pt] node[pos=0.1] {$0,1$};
\addplot{3*x^2}[yshift=8pt] node[pos=0.1] {$0,1$};
\end{axis}
\end{tikzpicture}
\end{figure}

\end{document}


With the example linked by Jake I adapted the file. Now it is producing the return value 1 and no good result. What is wrong?

\documentclass{article}
\usepackage{pgfplots}

\begin{document}

\begin{figure}
\begin{tikzpicture}
\begin{axis}
\addplot[yshift=8pt,add node at x={-4}{$0,1$}] {-x};
\addplot[yshift=8pt,add node at x={-4}{$0,1$}] {x^2};
\addplot[yshift=8pt,add node at x={-4}{$0,1$}] {3*x^2};
\end{axis}
\end{tikzpicture}
\end{figure}

\end{document}

-
You can use the (axis cs:x,y) to use the axis coordinate system to place your nodes. –  percusse Jan 14 '13 at 22:42
Welcome to TeX.SE. To add to @percusse's comment: you need to place them separately form the \addplot via something like \node at (axis cs: 0,20) {$f(x)$}; which places the node at (0,20), for example. –  Peter Grill Jan 14 '13 at 22:43
Related/duplicate? pgfplots: Placing node on a specific x-position –  Jake Jan 14 '13 at 23:33
With (axis cs:x,y) I place the note on a fix coordinate position. But I want to note the graph on a defined x position and the y position of the note is set by the function. I'm looking for something like node[xpos=-4]. –  Nils Jan 15 '13 at 11:26
@Nils: That's what the solution does that I linked to in my previous comment. –  Jake Jan 15 '13 at 12:02

You can use the code from the answer to pgfplots: Placing node on a specific x-position:

\documentclass{article}
\usepackage{pgfplots}
\usetikzlibrary{intersections}

\makeatletter
\def\parsenode[#1]#2\pgf@nil{%
\tikzset{label node/.style={#1}}
\def\nodetext{#2}
}

\tikzset{
add node at x/.style 2 args={
name path global=plot line,
/pgfplots/execute at end plot visualization/.append={
\begingroup
\@ifnextchar[{\parsenode}{\parsenode[]}#2\pgf@nil
\path [name path global = position line #1-1]
({axis cs:#1,0}|-{rel axis cs:0,0}) --
({axis cs:#1,0}|-{rel axis cs:0,1});
\path [xshift=1pt, name path global = position line #1-2]
({axis cs:#1,0}|-{rel axis cs:0,0}) --
({axis cs:#1,0}|-{rel axis cs:0,1});
\path [
name intersections={
of={plot line and position line #1-1},
name=left intersection
},
name intersections={
of={plot line and position line #1-2},
name=right intersection
},
label node/.append style={pos=1}
] (left intersection-1) -- (right intersection-1)
node [label node]{\nodetext};
\endgroup
}
}
}

\begin{document}

\begin{figure}
\begin{tikzpicture}
\begin{axis}
\addplot[add node at x={-4}{[fill=white]{$0,1$}}] {-x};
\addplot[add node at x={-4}{[fill=white]{$0,1$}}] {x^2};
\addplot[add node at x={-4}{[fill=white]{$0,1$}}] {3*x^2};
\end{axis}
\end{tikzpicture}
\end{figure}

\end{document}

-
That's the answer, thank you very much! :) –  Nils Jan 15 '13 at 21:27