maternCov: Matern covariance
In telefit: Estimation and Prediction for Remote Effects Spatial Process Models

This function evaluates the Matern covariance function for the elements of a (potentially non-square) spatial distance matrix

1	maternCov(d, scale = 1, range = 1, smoothness = 0.5, nugget = 0)

`d`	A numeric vector or matrix of distances at which the Matern correlation function should be evaluated.
`scale`	Scales correlations to covariances.
`range`	Matern range parameter. Controls the decay of pointwise correlations as a function of distance.
`smoothness`	Matern smoothness parameter. Controls the number of process derivatives.
`nugget`	Spatial covariance nugget.

data("coprecip")
attach(coprecip)

# compute spatial covariance matrix for an exponential covariance function
# using Colorado coordinates
Sigma = maternCov(fields::rdist.earth(coords.s), scale = 1, range = 250,
  smoothness = .5, nugget = 0)