swthresh {SpherWave}R Documentation

Thresholding of Spherical Wavelet Decomposition (‘swd’) Object

Description

This function performs various ways to threshold a `swd' class object.

Usage

swthresh(swd, policy, by.level, type, nthresh, value = 0.1, 
Q = 0.05) 

Arguments

swd an object of class `swd'
policy threshold technique. At present the possible policies are `"universal"', `"probability"', `"fdr"', `"Lorentz"' and `"sure"'.
by.level If FALSE, then perform a global threshold. If TRUE, a thresholding value is computed and applied separately to each resolution level.
type the type of thresholding. This can be `"hard"', `"soft"' or `"Lorentz"'.
nthresh the number of resolution levels to be thresholded in the decomposition
value the user supplied threshold represented by quantile level for `"probability"' policy
Q parameter for the false discovery rate of `"fdr"' policy

Details

This function thresholds or shrinks details stored in a `swd' object and returns the thresholded details in a modified `swd' object. For level-dependent thresholding, `"universal"', `"Lorentz"' and `"fdr"' are provided. Only hard type thresholding is proper for `"probability"' thresholding. Also note that only soft type thresholding is proper for `"sure"' thresholding.

Value

An object of class `swd'. This object is a list with the following components.

obs observations
latlon grid points of observation sites in degree
netlab vector of labels representing sub-networks
eta bandwidth parameters for Poisson kernel
method extrapolation methods, `"ls"' or `"pls"'
approx if TRUE, approximation is used.
grid.size grid size (latitude, longitude) of extrapolation site
lambda smoothing parameter for penalized least squares method
p0 starting level for extrapolation. Resolution levels p0+1, ..., L is used for extrapolation.
gridlon longitudes of extrapolation sites in degree
gridlat latitudes of extrapolation sites in degree
nlevels the number of multi-resolution levels
coeff interpolation coefficients
field extrapolation on grid.size
density1 density of SBF
latlim range of latitudes in degree
lonlim range of longitudes in degree
global List of successively smoothed data
density density of SW coefficients
detail List of details at different resolution levels
swcoeff spherical wavelet coefficients
thresh.info thresholding information and ranges of local components before thresholding

References

Oh, H-S. and Li, T-H. (2004) Estimation of global temperature fields from scattered observations by a spherical-wavelet-based spatially adaptive method. Journal of the Royal Statistical Society Ser. B, 66, 221–238.

See Also

sbf, swd, swr.

Examples

### Observations of year 1967
#data(temperature)
#names(temperature)

# Temperatures on 939 weather stations of year 1967    
#temp67 <- temperature$obs[temperature$year == 1967] 
# Locations of 939 weather stations    
#latlon <- temperature$latlon[temperature$year == 1967, ]

### Network design by BUD
#data(netlab)

### Bandwidth for Poisson kernel
#eta <- c(0.961, 0.923, 0.852, 0.723, 0.506)

### SBF representation of the observations by pls
#out.pls <- sbf(obs=temp67, latlon=latlon, netlab=netlab, eta=eta, 
#    method="pls", grid.size=c(50, 100), lambda=0.89)

### Decomposition
#out.dpls <- swd(out.pls)

### Thresholding
#out.univ <- swthresh(out.dpls, policy="universal", by.level=TRUE, 
#    type="hard", nthresh=4) 

[Package SpherWave version 1.1.0 Index]