I would like to have this coordinate system (with numbers on the axes):

I know how to make it in Tikz; but the numbers on the axes are missing and I would like to add a plot:
\documentclass[border=10pt, tikz]{standalone}
\usepackage{pgfplots}
\usetikzlibrary{arrows,positioning}
\begin{document}
\tikzset{
>=stealth',
punkt/.style={
rectangle,
rounded corners,
draw=black, very thick,
text width=6.5em,
minimum height=2em,
text centered},
pil/.style={
->,
thick,
shorten <=2pt,
shorten >=2pt,}
}
\begin{tikzpicture}
\draw [pil] (4,0) -- (4,8);
\draw [pil] (0,4) -- (8,4);
\draw [gray, dashed, very thin] (0,0) grid (8,8);
\end{tikzpicture}
\end{document}
The equation of the plot:
((x/7)^2*sqrt(abs(abs(x)-3)/(abs(x)-3))+(y/3)^2*sqrt(abs(y+3/7*sqrt(33))/(y+3/7*sqrt(33)))-1)
I don't know how to add numbers on the x- and y-axis. And I don't know how to plot the graph.
Kind regards!

pgfplotswould be a better choice here. Would you be willing to switch? – Gonzalo Medina Jul 02 '15 at 23:58