Combine bar chart with line chart on two Y-axes

Question

I want to combine two Y-axes into one figure. I'm using \pgfplotstableread for my data and I have a style for my bar charts. My code is:

\PassOptionsToPackage{table,dvipsnames,svgnames}{xcolor}
\documentclass[11pt, twoside, a4paper]{report}
\usepackage[inner = 30mm, outer = 20mm,  top = 30mm, bottom = 20mm, headheight = 13.6pt]{geometry}
\usepackage{tikz}
\usepackage[pdfpagelayout=TwoPageRight]{hyperref}
\usepackage[export]{adjustbox}
%\usepackage{showframe}
\hypersetup{colorlinks=true, linktoc=all, allcolors=green!30!black,}
\usepackage{subfig}
\usepackage{pgfplots}
\pgfplotsset{
    compat=1.16,
    % created a style for the common `axis' options
    my axis style/.style={
        width=\linewidth,
        height=0.35\linewidth,
        bar width=0.9,
        enlarge x limits={abs=0.45},    % <-- changed to absolute coordinates
        ymin=0,
        legend style={
            at={(0.5,1.05)},    % <-- adapted
            anchor=south,       % <-- changed from `north'
            legend columns=2,
        },
        ylabel={PR\textsubscript{A}},
        xtick=data,
        axis lines*=left,
        ymajorgrids,
        %
        table/x=x,
    },
    % created a style for the common `ybar' options
    my ybar style/.style={
        ybar,
        my ybar legend,            % <-- change legend image accordingly
        #1!50!black,
        fill=white!70!black,
        nodes near coords,      % <-- moved from `axis' options here
        % state absolute positions for the `nodes near coords'
        scatter/position=absolute,
        node near coords style={
            % state where the nodes should appear
            at={(\pgfkeysvalueof{/data point/x},0.5)},
            anchor=center,
            % make the font a bit smaller
            font=\footnotesize,
            % set the number format of the `nodes near coords'
            /pgf/number format/.cd,
            fixed,
            precision=2,
            zerofill,
        },
    },
    my ybar legend/.style={
        /pgfplots/legend image code/.code={
            \draw [
            ##1,
            /tikz/.cd,
            yshift=-0.25em,
            ] (0cm,0cm) rectangle (3pt,0.8em);
        },
    },
}

\pgfplotstableread{
    x   SP_CIGS SP_cSi   WC      T4T
    17  0.926   0.923   0.915   0.895
    18  0.940   0.921   0.912   0.887
    19  0.862   0.857   0.840   0.809
    20  0.849   0.867   0.845   0.809
    21  0.871   0.886   0.873   0.847
    22  0.894   0.880   0.868   0.848
    23  0.903   0.886   0.875   0.844
    24  0.885   0.888   0.877   0.854
    25  0.892   0.893   0.883   0.863
    26  0.837   0.826   0.812   0.775
    27  0.814   0.818   0.789   0.761
    28  0.818   0.857   0.840   0.789
    29  0.810   0.848   0.833   0.771
}{\loadedtablerefpr}

\pgfplotstableread{
x   SP_CIGS SP_cSi  WC  T4T
17  23.90   22.28   22.76   20.81
18  25.57   23.34   24.42   22.61
19  33.59   31.85   33.36   31.97
20  27.14   25.71   25.82   26.80
21  34.33   33.20   34.06   33.61
22  37.01   35.60   35.26   35.48
23  32.42   30.97   29.20   33.15
24  31.08   29.57   28.61   30.17
25  29.76   28.69   27.42   28.21
26  36.22   34.44   32.27   35.31
27  37.96   36.30   34.59   37.09
28  35.84   34.74   33.03   34.97
29  38.07   36.88   35.14   36.37
}{\loadedtablereftemp}

\begin{document}
\begin{figure}
    \subfloat[System 1]{%
        \begin{tikzpicture}
        \begin{axis}[
        my axis style,
        ]
        \addplot [
        my ybar style=red!50!black,
        ] table [y=SP_CIGS] {\loadedtablerefpr};
        \legend{PR\textsubscript{A} per week, Temperature}
        \end{axis}
        \begin{axis}[my axis style,]
        \addplot [draw=blue, ultra thick, smooth, y = SP_CIGS] table {\loadedtablereftemp};
        \end{axis}
        \end{tikzpicture}
    }

    \subfloat[System 2]{%
        \begin{tikzpicture}
        \begin{axis}[
        my axis style,
        ]
        \addplot [
        my ybar style=blue!50!black,
        ] table [y=SP_cSi] {\loadedtablerefpr};
        \end{axis}
        \begin{axis}[my axis style]
        \addplot [ultra thick, y = SP_cSi] table {\loadedtablereftemp};
        \end{axis}
        \end{tikzpicture}
    }

    \subfloat[System 3]{%
        \begin{tikzpicture}
        \begin{axis}[
        my axis style,
        ]
        \addplot [
        my ybar style=black,
        draw=black,  
        ] table [y=T4T] {\loadedtablerefpr};
        \end{axis}
        \begin{axis}[my axis style]
        \addplot [ultra thick, y = T4T] table {\loadedtablereftemp};
        \end{axis}
        \end{tikzpicture}
    }

    \subfloat[System 4]{%
        \begin{tikzpicture}
        \begin{axis}[
        my axis style,
        ]
        \addplot [
        my ybar style=green!50!black,
        ] table [y=WC] {\loadedtablerefpr};
        \end{axis}
        \begin{axis}[my axis style]
        \addplot [ultra thick, y = WC] table {\loadedtablereftemp};
        \end{axis}
        \end{tikzpicture}
    }
    \caption{Caption}
    \label{fig:PRs ref syst}
\end{figure}
\end{document} 

And the result is this (only showing the first of four graphs, because they're all similar):

I would like to fix the following problems:

• The x ticks look bold, I think because it draws them twice
• The secondary Y axis overlaps the first one (second should be on the right)
• The secondary Y axis should have \degree C as label
• The secondary y tick lines (not sure what they're called) overlap the bars
• The secodary y tick lines do not use the same steps as the primary (I would like to have them be the same amount of steps)

Does anyone have any ideas? :)

Answer 1

Make a new style for the secondary axes, e.g.

% new style for axis on right
my axis style 2/.style={
    my axis style, % inherit from first style
    axis lines*=right, % move yaxis line to right side
    xticklabels={}, % no labels on x-axis
    ylabel=$^{\circ}$C,
    tickwidth=0pt, % hides ticks
    ymin=0,ymax=50,
    ytick distance=10,
    grid=none % turn off grid
},

I set ymin, ymax and ytick distance also for the first axis style, to force ticks at the same heights. (There are quite possibly more elegant solutions to this problem.)

To avoid having the temperature plot on top of the numbers, you can shift those numbers down with at={(\pgfkeysvalueof{/data point/x},0.3)} instead of at={(\pgfkeysvalueof{/data point/x},0.5)} in the nodes near coords style in my ybar style.

I also used \addlegendimage to add a thick black line for the temperature to the legend, though that is a bit misleading when it's blue in the first plot.

\PassOptionsToPackage{table,dvipsnames,svgnames}{xcolor}
\documentclass[11pt, twoside, a4paper]{report}
\usepackage[inner = 30mm, outer = 20mm,  top = 30mm, bottom = 20mm, headheight = 13.6pt]{geometry}
\usepackage[pdfpagelayout=TwoPageRight]{hyperref}
\usepackage[export]{adjustbox}
%\usepackage{showframe}
\hypersetup{colorlinks=true, linktoc=all, allcolors=green!30!black,}
\usepackage{subfig}
\usepackage{pgfplots} % loads tikz
\pgfplotsset{
    compat=1.16,
    % created a style for the common `axis' options
    my axis style/.style={
        width=\linewidth,
        height=0.35\linewidth,
        bar width=0.9,
        enlarge x limits={abs=0.45},    % <-- changed to absolute coordinates
        ymin=0,
        legend style={
            at={(0.5,1.05)},    % <-- adapted
            anchor=south,       % <-- changed from `north'
            legend columns=2,
        },
        ylabel={PR\textsubscript{A}},
        xtick=data,
        axis lines*=left,
        ymajorgrids,
        %
        table/x=x,
        ymin=0,ymax=1,
        ytick distance=0.2
    },
    % new style for axis on right
    my axis style 2/.style={
        my axis style,
        axis lines*=right,
        xticklabels={},
        ylabel=$^{\circ}$C,
        tickwidth=0pt,
        ymin=0,ymax=50,
        ytick distance=10,
        grid=none
    },
    % created a style for the common `ybar' options
    my ybar style/.style={
        ybar,
        my ybar legend,            % <-- change legend image accordingly
        #1!50!black,
        fill=white!70!black,
        nodes near coords,      % <-- moved from `axis' options here
        % state absolute positions for the `nodes near coords'
        scatter/position=absolute,
        node near coords style={
            % state where the nodes should appear
            at={(\pgfkeysvalueof{/data point/x},0.3)},
            anchor=center,
            % make the font a bit smaller
            font=\footnotesize,
            % set the number format of the `nodes near coords'
            /pgf/number format/.cd,
            fixed,
            precision=2,
            zerofill,
        },
    },
    my temp plot/.style={
       ultra thick,
       black
    },
    my ybar legend/.style={
        /pgfplots/legend image code/.code={
            \draw [
            ##1,
            /tikz/.cd,
            yshift=-0.25em,
            ] (0cm,0cm) rectangle (3pt,0.8em);
        },
    },
}

\pgfplotstableread{
    x   SP_CIGS SP_cSi   WC      T4T
    17  0.926   0.923   0.915   0.895
    18  0.940   0.921   0.912   0.887
    19  0.862   0.857   0.840   0.809
    20  0.849   0.867   0.845   0.809
    21  0.871   0.886   0.873   0.847
    22  0.894   0.880   0.868   0.848
    23  0.903   0.886   0.875   0.844
    24  0.885   0.888   0.877   0.854
    25  0.892   0.893   0.883   0.863
    26  0.837   0.826   0.812   0.775
    27  0.814   0.818   0.789   0.761
    28  0.818   0.857   0.840   0.789
    29  0.810   0.848   0.833   0.771
}{\loadedtablerefpr}

\pgfplotstableread{
x   SP_CIGS SP_cSi  WC  T4T
17  23.90   22.28   22.76   20.81
18  25.57   23.34   24.42   22.61
19  33.59   31.85   33.36   31.97
20  27.14   25.71   25.82   26.80
21  34.33   33.20   34.06   33.61
22  37.01   35.60   35.26   35.48
23  32.42   30.97   29.20   33.15
24  31.08   29.57   28.61   30.17
25  29.76   28.69   27.42   28.21
26  36.22   34.44   32.27   35.31
27  37.96   36.30   34.59   37.09
28  35.84   34.74   33.03   34.97
29  38.07   36.88   35.14   36.37
}{\loadedtablereftemp}

\begin{document}
\begin{figure}
    \subfloat[System 1]{%
        \begin{tikzpicture}
        \begin{axis}[
        my axis style,
        ]
        \addplot [
        my ybar style=red!50!black,
        ] table [y=SP_CIGS] {\loadedtablerefpr}; \ref{bars}

        \addlegendimage{my temp plot}
        \legend{PR\textsubscript{A} per week, Temperature}
        \end{axis}
        \begin{axis}[my axis style 2]
        \addplot [my temp plot, draw=blue, smooth, y = SP_CIGS] table {\loadedtablereftemp};
        \end{axis}
        \end{tikzpicture}
    }

    \subfloat[System 2]{%
        \begin{tikzpicture}
        \begin{axis}[
        my axis style,
        ]
        \addplot [
        my ybar style=blue!50!black,
        ] table [y=SP_cSi] {\loadedtablerefpr};
        \end{axis}
        \begin{axis}[my axis style 2]
        \addplot [my temp plot, y = SP_cSi] table {\loadedtablereftemp};
        \end{axis}
        \end{tikzpicture}
    }

    \subfloat[System 3]{%
        \begin{tikzpicture}
        \begin{axis}[
        my axis style,
        ]
        \addplot [
        my ybar style=black,
        draw=black,  
        ] table [y=T4T] {\loadedtablerefpr};
        \end{axis}
        \begin{axis}[my axis style 2]
        \addplot [my temp plot, y = T4T] table {\loadedtablereftemp};
        \end{axis}
        \end{tikzpicture}
    }

    \subfloat[System 4]{%
        \begin{tikzpicture}
        \begin{axis}[
        my axis style,
        ]
        \addplot [
        my ybar style=green!50!black,
        ] table [y=WC] {\loadedtablerefpr};
        \end{axis}
        \begin{axis}[my axis style 2]
        \addplot [my temp plot, y = WC] table {\loadedtablereftemp};
        \end{axis}
        \end{tikzpicture}
    }
    \caption{Caption}
    \label{fig:PRs ref syst}
\end{figure}
\end{document}