Language Reference

WAVGET Call

extracts wavelet information

CALL WAVGET( result, decomp, request <, options> );

The WAVGET subroutine is used to return information that is encoded in a wavelet decomposition.

The required inputs are

decomp

specifies a wavelet decomposition that has been computed by using a call to the WAVFT subroutine.

request

specifies a scalar indicating what information is to be returned.

You can specify different optional arguments depending on the value of request:

request=1

requests the number of points in the input data vector.

result

returns as a scalar containing this number.

request=2

requests the detail coefficients at a specified level. Valid syntax is

CALL WAVGET( result, decomp, 2, level <, opt> );

where the argument

level

is the level at which the detail coefficients are requested.

opt

is an optional vector which specifies the thresholding to be applied to the returned detail coefficients. See the WAVIFT subroutine call for details. If you omit this argument, no thresholding is applied.

result

returns as a column vector containing the specified detail coefficients.

request=3

requests the scaling coefficients at a specified level. Valid syntax is

CALL WAVGET( result, decomp, 3, level <, opt> );

where the argument

level

is the level at which the scaling coefficients are requested.

opt

is an optional vector that specifies the thresholding to be applied. See the WAVIFT subroutine call for a description of this vector. The scaling coefficients at the requested level are obtained by using the inverse wavelet transform, after applying the specified thresholding. If you omit this argument, no thresholding is applied.

result

returns as a column vector containing the specified scaling coefficients.

request=4

requests the thresholding status of the detail coefficients in decomp.

result

returns as a scalar whose value is

0,

if the detail coefficients have not been thresholded

1,

otherwise

request=5

requests the wavelet options vector that you specified in the WAVFT subroutine call to compute decomp.

result

returns as a column vector with 4 elements containing the specified options vector. See the WAVFT subroutine call for the interpretation of the vector entries.

request=6

requests the index of the top level in decomp.

result

returns as a scalar containing this number.

request=7

requests the index of the lowest level in decomp.

result

returns as a scalar containing this number.

request=8

requests a vector evaluating the father wavelet used in decomp, at an equally spaced grid spanning the support of the father wavelet. The number of points in the grid is specified as a power of 2 times the support width of the father wavelet. For wavelets in the Daubechies extremal phase and least asymmetric families, the support width of the father wavelet is , where is the family member. Valid syntax is

CALL WAVGET( result, decomp, 8 <, power> );

where the optional argument

power

is the exponent of 2 determining the number of grid points used. power defaults to 8 if you do not specify this argument.

result

returns as a column vector containing the specified evaluation of the father wavelet.

An example is available in the documentation for the WAVFT subroutine.