Drawing arrow heads without the tails in TikZ?

Question

I have an ellipse in a TikZ diagram and I would like to indicate a direction using an arrow head, but do not wish to draw the path leading up to the arrow head.

I currently have

\draw[->] (0,2) arc (90:45:1 and 2);
\draw (0,0) ellipse (1 and 2);

but I'd like the arc leading up to the arrow to be invisible (so it is not redrawing over the ellipse), so that it's just the head showing.

What is the best way to achieve this?

Answer 1

You can use path decorations:

\documentclass{article}
\usepackage{tikz}

\usetikzlibrary{decorations.markings}

\begin{document}

\begin{tikzpicture}[decoration={
  markings,
  mark=at position 0.2 with {\arrow{<}}}
]
  \draw[postaction={decorate}] (0,0) ellipse (1 and 2);
\end{tikzpicture}

\end{document}

Answer 2

Any easy to type but slightly hackish solution is to use a very small path for the arrow:

\begin{tikzpicture}
    \draw (0,0) ellipse (1 and 2);
    \draw[->] (0,0) ++ (45:1 and 2) arc (45:44.9:1 and 2);
\end{tikzpicture}

To get a flexible "clean" solution one can use markings:

\usetikzlibrary{decorations.markings}
\begin{tikzpicture}
    \draw (0,0) ellipse (1 and 2);
    \draw[decoration={markings,mark=at position 1 with {\arrow{>}}},decorate]
        (0,2) arc (90:45:1 and 2);
\end{tikzpicture}

The marking can also be directly applied to the ellipse (which is drawn counterclockwise from 0 degrees):

\begin{tikzpicture}
    \draw [decoration={markings,mark=at position 1/8 with {\arrowreversed{>}}},postaction={decorate}] 
        (0,0) ellipse (1 and 2);
\end{tikzpicture}

See Section 27.6 of the TikZ manual for the general syntax of the mark option.