computes the density function of a gaussian process
GaussianDensity(res, SS, invSS, logabsdetSS)
y vector of density (1 x T)
matrix of residuals (N x T)
covariance matrice or array of covariance matrices (N x N) or (N x N x T)
Inverse of SS (N x N) or (N x N x T) - optional input
log(abs(|SS|)) (1 x T) - optional input
This function is based on the "Gaussian" function by Le and Singleton (2018).
"A Small Package of Matlab Routines for the Estimation of Some Term Structure Models."
(Euro Area Business Cycle Network Training School - Term Structure Modelling).
Available at: https://cepr.org/40029