smooth.sspline {sspline}R Documentation

Smoothing Spline on the Sphere

Description

It fits a smoothing splines on the sphere with the smoothing parameter chosen by the generalized cross validation (GCV) criteria or given by the user.

Usage

smooth.sspline(lon, lat, y, m = 2, smth = 0, lambda = 0)

Arguments

lon numeric vector, the longitudes
lat numeric vector, the latitudes
y numeric vector, the observations at (lon, lat)
m integer, order of smoothing, takes value from 1 to 10. Default to 2
smth method for choosing the smoothing parameter: 0, gcv method; 1, user specified. Default to 0
lambda used only when smth = 1.

Details

It calls Fortran subroutine with the .Fortran interface.

Value

A smooth.sspline object with the components

lon the original longitude
lat the original latitude
obs the original observation
lambda the lambda that minimizes the gcv score
gcv the corresponding gcv value at lambda
varhat the estimated variance
c the coefficient vector c for the estimated function
d the coefficient d for the estimated function
yhat the estimated (smoothed) observation
call the call to smooth.sspline

Note

The longitudes and latitudes are measured in degrees.

Author(s)

Xianhong Xie

References

Grace Wahba (1981), Spline Interpolation and Smoothing on the Sphere, SIAM J. SCI. STAT. COMPUT.

Examples

data(WTdiff)

subdat <- WTdiff[sample(nrow(WTdiff), 200), 2:4]
attach(subdat)

smooth.sspline(lon, lat, avgd)

detach(subdat)

[Package sspline version 0.1-5 Index]