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nullevels.imwd
Sets whole resolution levels of coefficients equal to zero in a
imwd object.
DESCRIPTION
Sets whole resolution levels of coefficients equal to zero in a
imwd object.
USAGE
nullevels.imwd(imwd, levelstonull)
REQUIRED ARGUMENTS
- imwd
- An object of class imwd.
- levelstonull
- An integer vector specifying which resolution levels of coefficients of
imwd that you wish to set to zero.
OPTIONAL ARGUMENTS
None.
VALUE
An object of class imwd where the coefficients
in resolution levels specified by levelstonull have been
set to zero.
SIDE EFFECTS
None
DETAILS
Setting whole resolution levels of coefficients to zero can be very
useful. For example, one can construct a linear smoothing method by
setting all coefficients above a particular resolution (the
primary resolution equal to zero. Also setting particular
levels equal to zero can also be useful for removing noise which is
specific to a particular resolution level (as long as important signal
is not also contained at that level).
Note that this function removes the horiztonal, diagonal and
vertical detail coefficients at the resolution level specified.
It does not remove the father wavelet coefficients at those resolution
levels.
To remove individual coefficients on a systematic basis you probably
want to look at the threshold function.
RELEASE
Version 3.9.5 Copyright Guy Nason 1998
SEE ALSO
nullevels,
imwd,
imwd object,
threshold.
EXAMPLES
#
# Do the wavelet transform of the Lennon image
#
> lenimwd <- imwd(lennon)
#
# Set scales (resolution levels) 2, 4 and 6 equal to zero.
#
> lenwdNL <- nullevels(lenimwd, levelstonull=c(2,4,6))
#
# Now let's plot the coefficients using a nice blue-heat colour map
#
# You will see that coefficients at levels 2, 4 and 6 are black (i.e. zero)
# You can see that coefficients at other levels are unaffected and still
# show the Lennon coefficients.
#
> plot(lenwdNL)
