This function computes the value of the Epanechnikov kernel for a given input \(u\).
The Epanechnikov kernel is a popular choice in kernel density estimation due to its optimal
properties in minimizing mean integrated squared error.
Usage
epanechnikov_kernel(u)
Value
A numeric vector of kernel values corresponding to each input u.
Arguments
u
A numeric vector of points at which the kernel is evaluated.
Details
The Epanechnikov kernel is defined as:
$$
K(u) = \begin{cases}
\frac{3}{4}(1 - u^2) & \text{if } |u| \leq 1, \\
0 & \text{otherwise}.
\end{cases}
$$
This function applies the above formula to each element of the input vector u.