ramps (version 0.6-2)

corRRatio: Rational Quadratic Spatial Correlation Structure

Description

This function is a constructor for the 'corRRatio' class, representing a rational quadratic spatial correlation structure. Letting $r$ denote the range, the correlation between two observations a distance $d$ apart is $1/(1+(d/r)^2)$.

Usage

corRRatio(value = numeric(0), form = ~ 1,
             metric = c("euclidean", "maximum", "manhattan", "haversine"),
             radius = 3956)

Arguments

value

optional numeric range parameter value for the rational quadratic correlation structure, which must be greater than zero. Defaults to numeric(0), which results in a range of 90% of the minimum distance being assigned to the

form

one-sided formula of the form ~ S1+...+Sp, specifying spatial covariates S1 through Sp. Defaults to ~ 1, which corresponds to using the order of the observations in the data as a covariate.

metric

optional character string specifying the distance metric to be used. The currently available options are "euclidean" for the root sum-of-squares of distances; "maximum" for the maximum difference; "manhattan" for t

radius

radius to be used in the haversine formula for great-circle distance. Defaults to the Earth's radius of 3,956 miles.

Value

• Object of class 'corRRatio', also inheriting from class 'corSpatial', representing a rational quadratic spatial correlation structure.

References

Cressie, N.A.C. (1993), Statistics for Spatial Data, J. Wiley & Sons.

Venables, W.N. and Ripley, B.D. (1997) Modern Applied Statistics with S-plus, 2nd Edition, Springer-Verlag.

See Also

corClasses, Initialize.corStruct, summary.corStruct

Examples

sp1 <- corRRatio(form = ~ x + y + z)

spatDat <- data.frame(x = (0:4)/4, y = (0:4)/4)

cs1Ratio <- corRRatio(1, form = ~ x + y)
cs1Ratio <- Initialize(cs1Ratio, spatDat)
corMatrix(cs1Ratio)

cs2Ratio <- corRRatio(1, form = ~ x + y, metric = "man")
cs2Ratio <- Initialize(cs2Ratio, spatDat)
corMatrix(cs2Ratio)