Returns an element related to an integral of a derivative of the desired kernel. See references for details.
d1(X, x, sigma, type)The scalar value given the integrated derivative.
The design matrix
The point at which to evaluate.
The error variance of the model.
A string, one of "Gaussian", "Matern5_2", and "Matern3_2" indicating the covariance kernel to use.
Mickael Binois, Robert B. Gramacy, Michael Ludkovski (2017), Practical Heteroscedastic Gaussian Process Modeling for Large Simulation Experiments, Journal of Computational and Graphical Statistics