wavethresh (version 2.2-3)

wr: Discrete wavelet transform (reconstruction).

Description

This function performs the reconstruction stage of Mallat's pyramid algorithm, i.e., the discrete inverse wavelet transform.

Usage

wr(wd.object, start.level=0, verbose=FALSE, return.object=FALSE)

Arguments

wd.object

A wavelet decomposition object as returned by wd, see wd.object.

start.level

integer; the level at which to start reconstruction. This is usually the first (level 0).

verbose

logical, controlling the printing of "informative" messages whilst the computations progress. Such messages are generally annoying so it is turned off by default.

return.object

logical; If this is FALSE then the top level of the reconstruction is returned (this is the reconstructed function at the highest resolution). Otherwise if it is T the whole wd reconstructed object is returned.

Value

• Either a vector containing the top level reconstruction or an object of class "wd" containing the results of the reconstruction, details to be found in help for "wd.object".

Side Effects

The appropriate C object code is loaded if it isn't.

code

accessC(wd.object, level=wd.object$levels)

RELEASE

Release 2.2 Copyright Guy Nason 1993

Details

The code implements Mallat's pyramid algorithm (Mallat 1989). In the reconstruction the quadrature mirror filters G and H are supplied with c0 and d0, d1, ...

References

see wd for a list.

See Also

wd, accessC, accessD, filter.select, threshold.

Examples

# Decompose and then exactly reconstruct test.data
example(wd)#-> wds has wd() ressult
rec.wds <- wr(wds)
rec.wds.obj <- wr(wds, return.object = TRUE)
rec.wds2 <- accessC(rec.wds.obj, level=rec.wds.obj$nlevels)
all(rec.wds == rec.wds2)# since wr() internally uses accessC()

# Look at accuracy of reconstruction
summary(abs(rec.wds - y)) #~ 10^-11

# Reconstruct a hard.thresholded object, look at the wavelet coefficients
summary(thr.wds <- wr(threshold(wds, type="hard") ))