quadHSIC: Determines the quadratic form of the HSIC unbiased estimator
Description
For a linear kernel of the outcome \(L = Y^\top Y\), the unbiased HSIC
estimator implemented in HSIC can be expressed as a quadratic
form of the outcome \(Y\) i.e. \(HSIC(K, L) = Y^\top Q(K) Y\). Here,
the matrix \(Q\) only depends on the kernel similarity matrix \(K\).