Builds a spatial correlation matrix using an RBF kernel with a nugget
term for numerical stability. Distances are Euclidean in the coordinate
units (see get_spatial_distance()), so length_scale is in those same
units.
Usage
space_kernel(coordinates, length_scale, nugget = 1e-09)
Arguments
- coordinates
A data frame with columns lon and lat.
- length_scale
A positive numeric scalar for the spatial length-scale.
- nugget
A non-negative numeric scalar added to the diagonal for
numerical stability.
Value
A positive-definite matrix representing spatial correlation.