Draw line between two plots

Question

I am trying to draw a line between points of two plots as shown in the picture (the blue line) but without luck. It is with tikzpicture and pgfplots. Similar to:

\begin{tikzpicture}
\begin{axis}
  \addplot coordinates { (1,2) (2,3) };
  \addplot coordinates { (1,4) (2,6) };
\end{axis}
\end{tikzpicture}

I did try adding nodes to \addplot but they seem to be located at (0,0) regardless of settings.

Any suggestions?

Answer 1

The pgfplots package introduces an own coordinate system that allows you to use the diagram's coordinates with normal tikZ drawing commands. Just put an axis cs: before your coordinates as in

\draw (axis cs:1,0) -- (axis cs:2,0);

The following code below shows your code expanded with a line drawn from the points (2,3) to (2,6):

\documentclass{standalone}
\usepackage{tikz}
\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}
\begin{axis}
    \addplot coordinates { (1,2) (2,3) };
    \addplot coordinates { (1,4) (2,6) };
    \draw (axis cs:2,3) -- node[left]{Text} (axis cs:2,6);
\end{axis}
\end{tikzpicture}
\end{document}