PGFPlots: How do I add a legend to a plot drawn manually (not using \addplot)?

Question

I'm making a plot using rectangles that I drew manually, instead of using the standard plot types defined in PGFPlots. Here is an MWE:

\documentclass{standalone}
\usepackage{pgfplots} 
\pgfplotsset{compat=newest}
\begin{document}
\begin{tikzpicture} 
\begin{axis}[xmin=0,xmax=5,ymin=0,ymax=4]
\draw[fill=blue!50] (0,0) rectangle (1,1);
\draw[fill=green!50] (1,0) rectangle (4,3);
\draw[fill=red!50] (4,0) rectangle (5,2);
\end{axis} 
\end{tikzpicture}
\end{document}

Question: How do I add a legend to the plot? I want to label each of the three rectangles, e.g., rectangle 1 "blue", rectangle 2 "green", and rectangle 3 "red".

You could add a node (or three nodes) in the top right corner of your drawing, with the information you need in the node's curly brackets. — Daniel N, Jun 22 '21 at 04:53
@DanielN I'm not sure what you mean, could you please provide an example? — I Like to Code, Jun 22 '21 at 08:11
See https://tex.stackexchange.com/questions/54794/using-a-pgfplots-style-legend-in-a-plain-old-tikzpicture/148855?r=SearchResults&s=1|56.7385#148855 — John Kormylo, Jun 22 '21 at 12:29

score 3 · Accepted Answer · answered Jun 22 '21 at 13:50

3

You can use \addlegendimage:

\documentclass{standalone}
\usepackage{pgfplots} 
\pgfplotsset{compat=newest}
\begin{document}
\begin{tikzpicture} 
\begin{axis}[xmin=0,xmax=5,ymin=0,ymax=4]
\draw[fill=blue!50] (0,0) rectangle (1,1);
\draw[fill=green!50] (1,0) rectangle (4,3);
\draw[fill=red!50] (4,0) rectangle (5,2);
\addlegendimage{area legend, fill=blue!50}
\addlegendimage{area legend, fill=green!50}
\addlegendimage{area legend, fill=red!50}
\legend{foo, bar, baz}
\end{axis} 
\end{tikzpicture}
\end{document}

answered Jun 22 '21 at 13:50

Torbjørn T.

206,688

Was this the type of legend you wanted, or did you just want to add text inside each rectangle? – Torbjørn T. Jun 22 '21 at 19:27
This is perfect actually, thank you! – I Like to Code Jun 23 '21 at 14:54

score 1 · Answer 2 · answered Jun 22 '21 at 10:36

Something like this?

I used tikz since you don't really need pgfplots, if I understand correctly your question.
In the node that gives the legend, I used two different elements...

The code

\documentclass[11pt, border=1cm]{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture} 
  \draw[blue, fill=blue!50] (0, 0) rectangle (1, 1);
  \draw[green, fill=green!50] (1, 0) rectangle (4, 3);
  \draw[red, fill=red!50] (4, 0) rectangle (5, 2);
% the legend
  \path (5, 5) node[draw, scale=.6, anchor=north west, text width=4.4em]
  {%
    $1$ = blue
    $2$ = green
    $3$ = \tikz{\draw[red, fill=red!50] (0, 0) rectangle (1em, 1.5ex);}
  };
% the axes
  \draw[->] (0, 0) -- (6, 0) node[below, scale=.8] {$x$};
  \draw[->] (0, 0) -- (0, 5) node[left, scale=.8] {$y$};
  \foreach \i in {1, ..., 5}{
    \draw (\i, 2pt) -- ++(0, -4pt) node[below, scale=.7] {$\i$};
  }
  \foreach \j in {1, ..., 4}{
    \draw (2pt, \j) -- ++(-4pt, 0) node[left, scale=.7] {$\j$};
  }
\end{tikzpicture}
\end{document}

You have a \tikz inside a tikzpicture. Sometimes this works, but I wouldn't rely on it. — John Kormylo, Jun 22 '21 at 12:14

score 1 · Answer 3 · answered Jun 22 '21 at 12:34

This uses a tabular inside a savebox to construct the legend.

Note that one really should but \sbox0 inside an environment or group to preserve its global contents.

\documentclass{standalone}
\usepackage{pgfplots} 
\pgfplotsset{compat=newest}
\begin{document}
\sbox0{\begin{tabular}{rl}
  \tikz{\node [fill=blue!50, inner sep=1ex]{};} & blue\
  \tikz{\node [fill=green!50, inner sep=1ex]{};} & green\
  \tikz{\node [fill=red!50, inner sep=1ex]{};} & red
\end{tabular}}
\begin{tikzpicture} 
\begin{axis}[xmin=0,xmax=5,ymin=0,ymax=4,name=border]
\draw[fill=blue!50] (0,0) rectangle (1,1);
\draw[fill=green!50] (1,0) rectangle (4,3);
\draw[fill=red!50] (4,0) rectangle (5,2);
\end{axis} 
\node[below=1cm, draw, rounded corners] at (border.south) {\usebox0};
\end{tikzpicture}
\end{document}

PGFPlots: How do I add a legend to a plot drawn manually (not using \addplot)?

3 Answers3

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