extracts a selected set of discrete wavelet transform (DWT) coefficients from the full set of coefficients stored in compact form, as computed by nag_mldwt_2d (c09ecc)
is intended to be used after a call to nag_mldwt_2d (c09ecc)
(two-dimensional DWT), which in turn should be preceded by a call to nag_wfilt_2d (c09abc)
(two-dimensional wavelet filter initialization). Given an initial two-dimensional data set
, a prior call to nag_mldwt_2d (c09ecc)
computes the approximation coefficients (at the highest requested level) and three sets of detail coeficients at all levels and stores these in compact form in a one-dimensional array c
. nag_wav_2d_coeff_ext (c09eyc)
can then extract either the approximation coefficients or one of the sets of detail coefficients at one of the levels into a matrix
. The dimensions of
depend on the level extracted and are available from the arrays dwtlvm
as returned by nag_mldwt_2d (c09ecc)
which contain the first and second dimensions respectively. See Section 2.1
in the c09 Chapter Introduction for a discussion of the two-dimensional DWT.
the following notation is used in this section:
- is the number of wavelet coefficients in the first dimension, which, at level ilev, is equal to as returned by a call to nag_mldwt_2d (c09ecc) transforming nwl levels.
- is the number of wavelet coefficients in the second dimension, which, at level ilev, is equal to as returned by a call to nag_mldwt_2d (c09ecc) transforming nwl levels.