Theoretical Distance Based Covariance Functions

DESCRIPTION:

Computes theoretical covariance function at supplied distance values. Models include exponential, spherical, and gaussian covariances.

USAGE:

exp.cov(distance, range, sill=1, nugget=0, eps=1.0e-7) 
spher.cov(distance, range, sill=1, nugget=0, eps=1.0e-7) 
gauss.cov(distance, range, sill=1, nugget=0, eps=1.0e-7) 

REQUIRED ARGUMENTS:

distance
a vector of distances to compute the covariance for.
range
the range value.

OPTIONAL ARGUMENTS:

sill
the sill value. This is the absolute sill, the variance (covariance at distance = 0) is sill + nugget.
nugget
the nugget effect.
eps
any distance less than eps will be set to nugget + sill.

VALUE:

a vector of covariance values at the supplied distances.

DETAILS:

These functions are used with the krige function.

SEE ALSO:

,

EXAMPLES:

dist <- seq(0,5,length=50) 
plot(dist,exp.cov(dist,range=2,nugget=.2),type='l')