A matrix where rows represent the standardized grids.
Arguments
grids
A matrix where rows represent grid points and columns are coordinates.
center
A vector of real numbers specifying the centroid parameters in the modified exponential squared kernel. The default value is NULL and set to the center of the grid points: apply(x,2,mean).
scale
A vector of positive numbers specifying the scale parameters in the modified exponential squared kernel. The default value is NULL and set to values such that grid points in a range of (-max_range,max_range) in each dimension.
max_range
A positive real number indicating the maximum range of the grid points to specify the scale parameter. The default value is NULL and set to 6.