What's the best way to get a discontinuity symbol on a line?

Question

I'm trying to create a diagram where some distance/data is skipped, and this is indicated on the axis by a small symbol, either a little zigzag or some diagonal lines, as shown in the below example images.

What's the best way to reproduce this symbol/styling in tikz? (On a side note, is any particular symbol considered standard, or is preferred over others?)

I am currently producing the axis of my diagram using the below code, and would like the symbol to appear at about the (-2,6) point.

\documentclass{article}
\usepackage{tikz}
\begin{document}
\begin{figure}
\begin{tikzpicture}
    \draw[black,ultra thick] [-stealth] (-2,0) -- (-2,14);
    \node[rotate=90,font=\Large,anchor=south] at (-2,7) {Energy};
\end{tikzpicture}
\end{figure}
\end{document}

pgfplots has a axis x discontinuity key, see the documentation "Axis Discontinuities". — Ulrike Fischer, Aug 16 '17 at 08:38
Thanks! I'll look into that. I'm also keen to know how the same thing can be achieved on a line in a diagram. — Ulysses, Aug 16 '17 at 08:59
Related (drawing a discontinuity symbol on a line): https://tex.stackexchange.com/q/18436/2552 — Jake, Aug 16 '17 at 10:00
So it turns out the axis discontinuity key from pgfplots is too limited, and doesn't allow any customisation in where it's placed, but it at least told me what the symbol is called, which allowed me to better search for other solutions, and I found these two related question, which could help, so I'll look into them in more detail: https://tex.stackexchange.com/questions/18436/draw-the-discontinuity-symbol-with-tikz https://tex.stackexchange.com/questions/46422/axis-break-in-pgfplots — Ulysses, Aug 16 '17 at 10:01
A pst-plot solution: https://tex.stackexchange.com/a/83144 — Ross, Aug 16 '17 at 10:33
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score 2 · Answer 1 · answered Aug 16 '17 at 12:16

On way that gives you a lot of freedom is to suppress (in part) the drawing of the axis, and to redraw it after the plot with decorations:

\documentclass{article}
\usepackage{pgfplots}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
 separate axis lines,
 x axis line style= { draw opacity=0 }]
\addplot[] {x^2};

%store coodinates
\path[-] (rel axis cs:0,0)     coordinate(botstart)
          --(rel axis cs:0.7,0)coordinate(interruptbotA)
         (rel axis cs:0.87,0)  coordinate(interruptbotB)
         --(rel axis cs:1,0)   coordinate(botstop);

\path[-] (rel axis cs:0,1)     coordinate(topstart)
         --(rel axis cs:0.7,1) coordinate(interrupttopA)
         (rel axis cs:0.87,1)  coordinate(interrupttopB)
         --(rel axis cs:1,1)   coordinate(topstop);
\end{axis}

%Draw the axis with a decoration:
\draw(botstart)-- (interruptbotA) decorate[decoration=zigzag]{--(interruptbotB)} -- (botstop);
\draw(topstart)-- (interrupttopA) decorate[decoration=zigzag]{--(interrupttopB)} -- (topstop);

\end{tikzpicture}

\end{document}

One can also draw inside the axis environment but then you probably will have to disable clipping.

score 0 · Accepted Answer · answered Aug 16 '17 at 13:18

I've managed to find a simplistic but effective solution, which I thought I'd share. Essentially I just replace the single line from my original code with three consecutive lines, with the middle one having a zigzag decoration. This produces the zigzag symbol that indicates a discontinuity of the line/graph. I don't know how to produce the other type of symbol, but since this solution gets the job done, I don't really care.

The important thing to note for anyone trying to adapt this for their own purposes, is that the segment length of the middle line needs to be equal to its length, which is determined from its start and end coordinates. This ensures the zigzag is only one wavelength.

\documentclass{article}
\usepackage{tikz}
\usepackage{pgfplots}
\begin{document}

    \begin{figure}
        \begin{tikzpicture}
        \draw[black,ultra thick] (-2,0) -- (-2,5.5);
        \draw[black,ultra thick,decorate,decoration={zigzag,segment length=3mm, amplitude=5pt}] (-2,5.5) -- (-2,5.8);
        \draw[black,ultra thick] [-stealth] (-2,5.8) -- (-2,14);
        \node[rotate=90,font=\Large,anchor=south] at (-2,7) {Energy};
        \end{tikzpicture}
    \end{figure}

\end{document}

What's the best way to get a discontinuity symbol on a line?

2 Answers2

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