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I use tabular legends for my graphs in pgfplots. At least three posts give ways to do that: Tabular like legend, Custom legend and Tabular legend. I like the syntax where a \label is given to the curves, called in a \matrix after \end{axis}.

However, I often need to define the legend entries "by hand" with \addlegendimage, which is then labeled and reference to. Here's an example:

\documentclass[border=5pt]{standalone}
\usepackage{pgfplots}
\usetikzlibrary{
    matrix,
}
\pgfplotsset{
    compat=newest,
    every axis plot post/.append style={
        every mark/.append style={solid},        % avoid dashed markers
    }
}

\begin{document}
\begin{tikzpicture}
\begin{axis}[
title={$y=a \cdot x + b$},
    xlabel=$x$,
    ylabel=$y$,
    ]
\addplot+[domain=-1:2, samples=10, mark=o, dashed] {1*x+1};
\addplot+[domain=-1:2, samples=10, mark=o, solid] {1*x+2};
\addplot+[domain=-1:2, samples=10, mark=square, dashed] {2*x+1};
\addplot+[domain=-1:2, samples=10, mark=square, solid] {2*x+2};

\addlegendimage{dashed}  % define by hand a legend image
\label{plot:dashed}      % label it
\addlegendimage{solid}
\label{plot:solid}
\addlegendimage{only marks, mark=o}
\label{plot:o}
\addlegendimage{only marks, mark=square}
\label{plot:square}
\coordinate (legend) at (axis description cs:1.03,1);
\end{axis}

\matrix[
    draw,
    matrix of nodes,
    anchor=north west,
]
at (legend) {
    Slope                   & $a$ & $1/a$   \\
    \ref{plot:o}            & 2   & 0.5     \\
    \ref{plot:square}       & 1   & 1       \\
    Origin                  & $b$ & $1/b$   \\
    \ref{plot:solid}        & 2   & 0.5     \\
    % call the image. It would better to create it by hand here, no? 
    \ref{plot:dashed}       & 1   & 1       \\
};

\end{tikzpicture}
\end{document}

tabular legend with addlegendimage

It sounds strange to define "by-hand" a \addlegendimage with a \label and then call it in the matrix with \ref.
As we're still in the tikzpicture, is there a command to directly generate the legend images within the matrix?

Community
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user122824
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  • Maybe http://tex.stackexchange.com/questions/348129/include-plotmarks-in-the-title-of-a-plot is related. There it is explained how you get the plot mark and I think you know how to draw a line, right ;) Please let us know if we can close this question as a duplicate or if we shall provide an answer here. – Stefan Pinnow Jan 12 '17 at 16:17
  • @StefanPinnow Yep, definitely closely related. I can't get the vertical centering right in the matrix, but that's another problem. Thanks for the link, you can close this question! – user122824 Jan 12 '17 at 16:45
  • I think the nodes are vertically and horizontally aligned by default, aren't they? But in case you don't find out yourself: You are free to ask (another) follow-up question ;) – Stefan Pinnow Jan 12 '17 at 19:03

0 Answers0