[Tex/LaTex] pgfplots: two y-axis with three plots and one legend

pgfplots

After googling about my problem, I came up with this two year old question here on TeX.SX.
I adopted the example from there having two plots in the first axis-environment and one plot in the second axis-environment as given below:

\documentclass{article}

    % UNITS
\usepackage{siunitx}
\sisetup{per=slash, load=abbr}

    % GRAPHICS
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{width=7cm,compat=1.3}

\begin{document}

\begin{tikzpicture}
\pgfplotsset{
    scale only axis,
    scaled x ticks=base 10:3,
    xmin=0, xmax=0.06
}

\begin{axis}[
  axis y line*=left,
  ymin=0, ymax=80,
  xlabel=x-axis,
  ylabel=y-axis 1,
]
\addplot[smooth,mark=x,red] 
  coordinates{
    (0,68.6)
    (0.0148,72) 
    (0.0295,68.6)
    (0.0441,53.4)
    (0.059,22.8) 
}; \label{plot_one}
%\addlegendimage{/pgfplots/refstyle=Hplot}\addlegendentry{plot 1}
\addplot[smooth,mark=o,green] 
  coordinates{
    (0,60)
    (0.0148,65) 
    (0.0295,73)
    (0.0441,49)
    (0.059,19) 
}; \label{plot_two}
%\addlegendentry{plot 2}
\end{axis}

\begin{axis}[
  axis y line*=right,
  axis x line=none,
  ymin=0, ymax=100,
  ylabel=y-axis 2
]
\addlegendimage{/pgfplots/refstyle=plot_one}\addlegendentry{plot 1}
\addplot[smooth,mark=*,blue] 
  coordinates{
    (0,0)
    (0.0148,48) 
    (0.0295,66)
    (0.0441,66)
    (0.059,45.0) 
}; \addlegendentry{plot 3}
\end{axis}

\end{tikzpicture}
\end{document}

There is a comment about my problem beneath the answer of the old question linked to above, but I do not get this hint working. So, how can I get one legend containing all three "descriptions" of the three plots?

Best Answer

A doubtless naïve possibility:

\documentclass{article}

    % UNITS
\usepackage{siunitx}
\sisetup{per=slash, load=abbr}

    % GRAPHICS
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{width=7cm,compat=1.3}

\begin{document}

\begin{tikzpicture}
\pgfplotsset{
    scale only axis,
    scaled x ticks=base 10:3,
    xmin=0, xmax=0.06
}

\begin{axis}[
  axis y line*=left,
  ymin=0, ymax=80,
  xlabel=x-axis,
  ylabel=y-axis 1,
]
\addplot[smooth,mark=x,red]
  coordinates{
    (0,68.6)
    (0.0148,72)
    (0.0295,68.6)
    (0.0441,53.4)
    (0.059,22.8)
}; \label{plot_one}

\addplot[smooth,mark=o,green]
  coordinates{
    (0,60)
    (0.0148,65)
    (0.0295,73)
    (0.0441,49)
    (0.059,19)
}; \label{plot_two}

\end{axis}

\begin{axis}[
  axis y line*=right,
  axis x line=none,
  ymin=0, ymax=100,
  ylabel=y-axis 2
]
\addlegendimage{/pgfplots/refstyle=plot_one}\addlegendentry{plot 1}
\addlegendimage{/pgfplots/refstyle=plot_two}\addlegendentry{plot 2}
\addplot[smooth,mark=*,blue]
  coordinates{
    (0,0)
    (0.0148,48)
    (0.0295,66)
    (0.0441,66)
    (0.059,45.0)
}; \addlegendentry{plot 3}
\end{axis}

\end{tikzpicture}
\end{document}

gives:

3 plots, 2 axes, 1 legend, 3 descriptions

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