# Circle using tikz and pgfplots package

I have been trying to obtain this

Since i am still an amateur at using the tikz package, i started somewhere. This is my bit of code, but all i am obtaining is this

 \usepackage{pgfplots}
\begin{document}
\begin{figure}
\begin{tikzpicture}
\begin{axis}[
ticks=none,
axis lines = middle,
axis line style={->},
ymin=0,
xmin=-3, xmax=3,
xlabel={$Y$},
ylabel={$\pi$},
axis equal image
]
\draw (axis cs:0,3) circle [blue, radius=1];
\end{axis}
\end{tikzpicture}
\end{figure}
\end{document}


I could really use some help, thanks.

• You do not need pgfplots to draw a circle: \documentclass[tikz,border=3.14mm]{standalone} \begin{document} \begin{tikzpicture} \draw (0,3) circle [blue, radius=1]; \end{tikzpicture} \end{document} – marmot Mar 19 at 20:10

Here is some code that do not use pgfplots and to which you can add your labels :

\documentclass[tikz,border=7pt]{standalone}
\pgfmathsetseed{8}
\begin{document}
\begin{tikzpicture}
% draw axes
\draw
(-4,0) edge[-latex] (4,0)
(0,-4) edge[-latex] (0,4)
(0,0)  edge[-latex] (35:2);
% random points
\foreach \i in {0,...,30}
\draw[fill=white] (4*rand,4*rand) circle(2pt);
% circle
\draw[red] (0,0) circle (2);
\foreach \i in {0,8,...,359}
\fill (\i:2) circle (1.5pt);
\end{tikzpicture}
\end{document}


As a starting point, using polar coordinates in pgfplots, the following code can help.

\documentclass[margin=3.14159mm]{standalone}
\usepackage{pgf,tikz,pgfplots}
\usepackage{amsmath}
\usetikzlibrary{calc,arrows}
\pgfplotsset{compat=1.12}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
ticks=none,
axis lines=center,
axis equal image,
enlargelimits=true,
ymin=-3,ymax=3,
xmin=-3, xmax=3,
xlabel=$Y$,
ylabel=$\pi$
]
\draw [-stealth] (0,0)--({\r*cos(25)},{\r*sin(25)})node[midway,above,sloped]{$\varepsilon_R$};