sigma_finder: sigma_finder: heuristic to find sigma for the Ng kernel
Description
This is a heuristic to find the sigma for the kernel from the Ng spectral clustering algorithm.
It returns a global sigma. It uses the mean K nearest neighbour distances of all samples to
determine sigma.
Usage
sigma_finder(mat, NN = 3)
Arguments
mat
Data frame or matrix: with points as columns, features as rows
NN
Numerical value: the number of nearest neighbours to use (default=3)