# Direction arrows on a circle [duplicate]

I would like to plot circle (or another curve) with positive direction (and show it wit arrows).

This plots the circle

\documentclass{article}
\usepackage{tikz}
\RequirePackage{pgfplots}
\usetikzlibrary{shapes}
\usetikzlibrary{decorations}
\usepackage{verbatim}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{5pt}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
xmin=-1.5,xmax=2.5,ymin=-1.5,ymax=1.5,
axis lines=center,
ticks=none,
unit vector ratio*=1 1 1,
]
\addplot [very thick, smooth, domain=(0:2*pi)] ({1.+cos(deg(x))},{sin(deg(x))});

\end{axis}
\end{tikzpicture}
\end{document}


And I want to add arrows like that

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## marked as duplicate by Claudio Fiandrino, mafp, Torbjørn T., Jubobs, T. VerronApr 16 '13 at 8:55

Have you checked this answer? – g.kov Apr 16 '13 at 6:58
– texenthusiast Apr 16 '13 at 7:15
– Torbjørn T. Apr 16 '13 at 8:15

This is your code with the addition of arrows and decorations.markings tikzlibraries plus a tikz style (redarrows.tikstyle) where the arrow heads are defined. The code lets you easily customize the color and the shape af the arrowheads. I used >, but if you like another style refer to the list contained in Is it possible to change the size of an arrowhead in TikZ/PGF? and just change the argument of \arrow inside the tikz style

\documentclass{article}

\usepackage{tikz}
\RequirePackage{pgfplots}
\usetikzlibrary{shapes}
\usetikzlibrary{decorations}
\usetikzlibrary{arrows,decorations.markings}         %new code

\usepackage{verbatim}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}

\setlength\PreviewBorder{5pt}

\begin{document}
\tikzset{               %new code
redarrows/.style={postaction={decorate},decoration={markings,mark=at position 0.1 with {\arrow[draw=red]{>}}},
decoration={markings,mark=at position -0.4 with {\arrow[draw=red]{>}}},}}
\begin{tikzpicture}
\begin{axis}[
xmin=-1.5,xmax=2.5,ymin=-1.5,ymax=1.5,
axis lines=center,
ticks=none,
unit vector ratio*=1 1 1,
]
\addplot [very thick, smooth, domain=(0:2*pi),redarrows] ({1.+cos(deg(x))},{sin(deg(x))});         %new code

\end{axis}
\end{tikzpicture}

\end{document}


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is it possible to place the arrows based on polar coordinates like 1) at (radius of circle, angle=45) and 2) at (radius of circle, angle=225) so that position of arrows does not get effected when radius increases ? – texenthusiast Apr 16 '13 at 8:30
It's possible that I'm completely missing your point, but if you draw the first arrow at position, say, 0.125, no matter how bigger or smaller the circle is the arrow will always point to the corresponding angle. – domenico Apr 16 '13 at 9:42

With PSTricks.

\documentclass[pstricks,border=12pt]{standalone}
\usepackage{pst-plot}
\begin{document}
\begin{pspicture}(-1,-3)(5,3)
\psaxes[labels=none,ticks=none,linecolor=gray](0,0)(-1,-3)(5,3)
\pscircle[dimen=middle](2.5,0){2}
\psset{arrows=->,arrowinset=0,arcsep=-1.5\pslinewidth,linecolor=red}
\psarc(2.5,0){2}{44}{46}
\psarc(2.5,0){2}{-136}{-134}
\end{pspicture}
\end{document}


## Warning:

I don't know how to change the arrow head color more elegantly.

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