ddencmp (Wavelet Toolbox)

Default values for de-noising or compression.

[THR,SORH,KEEPAPP,CRIT] = ddencmp(IN1,IN2,X)
[THR,SORH,KEEPAPP] = ddencmp(IN1,'wv',X)
[THR,SORH,KEEPAPP,CRIT] = ddencmp(IN1,'wp',X)

Description

ddencmp is a de-noising and compression oriented function.

ddencmp gives default values for all the general procedures related to de-noising and compression of one- or two-dimensional signals, using wavelets or wavelet packets.

[THR,SORH,KEEPAPP,CRIT] = ddencmp(IN1,IN2,X) returns default values for de-noising or compression, using wavelets or wavelet packets, of an input vector or matrix X, which can be a one- or two-dimensional signal. THR is the threshold, SORH is for soft or hard thresholding, KEEPAPP allows you to keep approximation coefficients, and CRIT (used only for wavelet packets) is the entropy name (see wentropy).

IN1 is 'den' or 'cmp'.

IN2 is 'wv' or 'wp'.

For wavelets (three output arguments):

[THR,SORH,KEEPAPP] = ddencmp(IN1,'wv',X) returns default values for de-noising (if IN1 = 'den') or compression (if IN1 = 'cmp') of X. These values can be used for wdencmp.

For wavelet packets (four output arguments):

[THR,SORH,KEEPAPP,CRIT] = ddencmp(IN1,'wp',X) returns default values de-noising (if IN1 = 'den') or compression (if IN1 = 'cmp') of X. These values can be used for wpdencmp.

Examples

% Generate Gaussian white noise. 
    init = 2055415866; randn('seed',init); 
    x = randn(1,1000);

% Find default values for wavelets (3 output arguments). 
% These values can be used for wdencmp with option 'gbl'.
    % default for de-noising: 
    % soft thresholding and appr. cfs. kept 
    % thr = sqrt(2*log(n)) * s
    % where s is an estimate of level noise. 
    [thr,sorh,keepapp] = ddencmp('den','wv',x) 

thr =
    3.8593
sorh =
s
keepapp =
    1

    % default for compression: 
    % hard thresholding and appr. cfs. kept 
    % thr = median(abs(detail at level 1)) if nonzero 
    % else thr = 0.05 * max(abs(detail at level 1)). 
    [thr,sorh,keepapp] = ddencmp('cmp','wv',x)

thr =
    0.7003
sorh =
h
keepapp =
    1

% Find default values for wavelet packets (4 output arguments). 
% These values can be used for wpdencmp.
    % default for de-noising: 
    % soft thresholding and appr. cfs. kept 
    % thr = sqrt(2*log(n*log(n)/log(2)))
    % the noise level is supposed to be equal to 1; 
    % default entropy is 'sure' criterion. 
    [thr,sorh,keepapp,crit] = ddencmp('den','wp',x) 
thr =
    4.2911

sorh =
h
keepapp =
    1
crit =
sure
    % default for compression. 
    % hard thresholding and appr. cfs. kept 
    % thr = median(abs(detail at level 1)) 
    % default entropy is 'threshold' criterion. 
    [thr,sorh,keepapp,crit] = ddencmp('cmp','wp',x)

thr =
    0.7003
sorh =
h
keepapp =
    1
crit =
threshold