smooth.sspline: Smoothing Spline on the Sphere

In sspline: Smoothing Splines 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

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

smooth.sspline(lon, lat, avgd)

detach(subdat)

Example output

Call:
  smooth.sspline(lon = lon, lat = lat, y = avgd)

Sample Size n: 200 
Order of Smooth: 2 
Smoothing Par: 0 
GCV Criteria: 16.08341 
Estimated Var: 0 

sspline documentation built on May 2, 2019, 2:17 a.m.