Gradient of the Scaling function (marginal in dimension k) of Xiong et al. with respect to eta
affineScalingGrad(X, knots, k)an n*d matrix standing for a design of n experiments in d-dimensional space
a (K+1) vector of knots parametrizing the transformation. The knots are here the same in all dimensions.
dimension of the input variables for which the gradient is calculated
Gradient at X of the scaling transformation of Xiong et al. with respect to eta. In the present version of the function, the gradient calculation is restricted to the case of 2 parameters by dimension (corresponding to the CovAffineScaling class).
Y. Xiong, W. Chen, D. Apley, and X. Ding (2007), Int. J. Numer. Meth. Engng, A non-stationary covariance-based Kriging method for metamodelling in engineering design.