naginterfaces.library.wav.dim1_sngl_fwd¶
- naginterfaces.library.wav.dim1_sngl_fwd(x, comm)[source]¶
dim1_sngl_fwd
computes the one-dimensional discrete wavelet transform (DWT) at a single level. The initialization functiondim1_init()
must be called first to set up the DWT options.For full information please refer to the NAG Library document for c09ca
https://support.nag.com/numeric/nl/nagdoc_30.2/flhtml/c09/c09caf.html
- Parameters
- xfloat, array-like, shape
contains the input dataset , for .
- commdict, communication object, modified in place
Communication structure.
This argument must have been initialized by a prior call to
dim1_init()
.
- Returns
- cafloat, ndarray, shape
contains the th approximation coefficient, , for .
- cdfloat, ndarray, shape
contains the th detail coefficient, , for .
- Raises
- NagValueError
- (errno )
On entry, is inconsistent with the value passed to the initialization function: , should be .
- (errno )
Either the initialization function has not been called first or array [‘icomm’] has been corrupted.
- (errno )
Either the initialization function was called with or array [‘icomm’] has been corrupted.
- Notes
dim1_sngl_fwd
computes the one-dimensional DWT of a given input data array, , for , at a single level. For a chosen wavelet filter pair, the output coefficients are obtained by applying convolution and downsampling by two to the input, . The approximation (or smooth) coefficients, , are produced by the low pass filter and the detail coefficients, , by the high pass filter. To reduce distortion effects at the ends of the data array, several end extension methods are commonly used. Those provided are: periodic or circular convolution end extension, half-point symmetric end extension, whole-point symmetric end extension or zero end extension. The number , of coefficients or is returned by the initialization functiondim1_init()
.
- References
Daubechies, I, 1992, Ten Lectures on Wavelets, SIAM, Philadelphia