2D Epanechnikov Kernel What is the equation for the $2D$ Epanechnikov Kernel?
The following doesn't look right when I plot it.
$$K(x) = \frac{3}{4} * \left(1 - \left(\left(\frac{x}{\sigma} \right)^2 + \left(\frac{y}{\sigma}\right)^2\right) \right)$$
I get this:


I have an equation for some p-D Epanechnikov Kernel.
Maybe you will find it useful.
$$
\begin{equation}
K(\hat{x})=\begin{cases} \frac{1}2C_p^{-1}(p
+2)(1-||\hat{x}||^2)&  ||\hat{x}||<1\\\\
0& \text{otherwise}
\end{cases}
\end{equation}
$$
while $\hat{x}$ is a vector with p dimensions and $C_p$ is defined as:
$$C_1 = 2;\  C_2=\pi,\  C_3=\frac{4\pi}3$$
would like to see an equation for $C_p$ for every p.
