[Tex/LaTex] Controlling the amplitude of the snake function in TikZ

decorationstikz-pgf

I have been using TikZ with some success, but I can't figure out why the following code doesn't produce anything:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.pathmorphing}
\begin{document}

    \begin{tikzpicture}
    \draw[decorate, decoration=snake, segment length=5mm, amplitude=15mm] (0,0) -- (10,10);
    \end{tikzpicture}

\end{document}

except the following error

Latex Error: ./untitled.tex:7 Package pgfkeys Error: I do not know
the key
'/tikz/amplitude' and I am going to ignore it. Perhaps you misspelled
it.

Were I to remove the amplitude option, this would compile. I just tried installing the very latest pgf-TikZ package, but that didn't change anything (the update went well, other features are working correctly). This leads me to believe that this option is somehow outdated, but I can't find anything to remedy this.

Does anyone know how to control the 'snake' amplitude in the latest TikZ package?

Best Answer

You are missing a pair of braces. The line should be written as

\draw[decorate, decoration={snake, segment length=5mm, amplitude=15mm}] (0,0) -- (10,10);

amplitude is an option to decoration and not to \path, therefore the braces.

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

The source of the difficulty is that ellipses are constructed in a particular way in TikZ. They are paths that start from the x-axis and proceed counter-clockwise around their centre. The vast majority of the time, the exact parametrisation doesn't matter. You appear to have found the one situation where it does!

In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
  #2%
  \pgf@xa=-\pgf@x
  \origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother

\tikzset{
  reversed ellipse/.style={
    ellipse,
    reverse the ellipse%
  },
  reverse the ellipse/.code={
    \let\pgfpathellipse=\revpgfpathellipse
  }
}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,0) {hello world};

\node[reversed ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,-2) {hello world};
\end{tikzpicture}

\end{document}

Here's the result:

rotated ellipse

(the arrow got clipped, but you can see where it lies)

[Tex/LaTex] Making TeXworks use tikz package

You can't use the TikZ library babel unless you have TikZ/PGF version 3.00 (or later).

Installing the new version over an older TeX Live is not recommended. Update your TeX distribution.

Best Answer

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

[Tex/LaTex] Making TeXworks use tikz package

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