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wfilters

Wavelet filters

Syntax

[Lo_D,Hi_D,Lo_R,Hi_R] = wfilters(wname)
[F1,F2] = wfilters(wname,type)

Description

example

[Lo_D,Hi_D,Lo_R,Hi_R] = wfilters(wname) returns the four low-pass and high-pass, decomposition and reconstruction filters associated with the orthogonal or biorthogonal wavelet wname.

[F1,F2] = wfilters(wname,type) returns the pair of type filters associated with the orthogonal or biorthogonal wavelet wname. For example, wfilters('db6','h') returns the pair of high-pass filters Hi_D and Hi_R associated with the db6 wavelet.

Examples

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Set the wavelet name.

wname = 'db5';

Compute the four filters associated with wavelet name given by the input character vector wname and plot the results.

[Lo_D,Hi_D,Lo_R,Hi_R] = wfilters(wname); 
subplot(221); stem(Lo_D); 
title('Decomposition low-pass filter'); 
subplot(222); stem(Hi_D); 
title('Decomposition high-pass filter'); 
subplot(223); stem(Lo_R); 
title('Reconstruction low-pass filter'); 
subplot(224); stem(Hi_R); 
title('Reconstruction high-pass filter'); 
xlabel('The four filters for db5')

Input Arguments

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Name of orthogonal or biorthogonal wavelet, specified as one of the values listed here.

Wavelet Families

Wavelets

Daubechies

'db1' or 'haar', 'db2', ..., 'db10', ..., 'db45'

Coiflets

'coif1', ..., 'coif5'

Symlets

'sym2', ..., 'sym8', ...,'sym45'

Fejer-Korovkin filters

'fk4', 'fk6', 'fk8', 'fk14', 'fk22'

Discrete Meyer

'dmey'

Biorthogonal

'bior1.1', 'bior1.3', 'bior1.5'
'bior2.2', 'bior2.4', 'bior2.6', 'bior2.8'
'bior3.1', 'bior3.3', 'bior3.5', 'bior3.7'
'bior3.9', 'bior4.4', 'bior5.5', 'bior6.8'

Reverse Biorthogonal

'rbio1.1', 'rbio1.3', 'rbio1.5'
'rbio2.2', 'rbio2.4', 'rbio2.6', 'rbio2.8'
'rbio3.1', 'rbio3.3', 'rbio3.5', 'rbio3.7'
'rbio3.9', 'rbio4.4', 'rbio5.5', 'rbio6.8'

Type of filter pair to return, specified as one of the values listed here.

typeDescription
'd'

Decomposition filters (Lo_D and Hi_D)

'r'

Reconstruction filters (Lo_R and Hi_R)

'l'

Low-pass filters (Lo_D and Lo_R)

'h'

High-pass filters (Hi_D and Hi_R)

Output Arguments

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Decomposition low-pass filter, returned as a real-valued vector, associated with the wavelet wname.

Decomposition high-pass filter, returned as a real-valued vector, associated with the wavelet wname.

Reconstruction low-pass filter, returned as a real-valued vector, associated with the wavelet wname.

Reconstruction high-pass filter, returned as a real-valued vector, associated with the wavelet wname.

Filter pair of requested type, returned, specified as one of the pairs of filters listed here.

typeDescriptionFilter Pair
'd'

Decomposition filters

Lo_D and Hi_D

'r'

Reconstruction filters

Lo_R and Hi_R

'l'

Low-pass filters

Lo_D and Lo_R

'h'

High-pass filters

Hi_D and Hi_R

References

[1] Daubechies, I. Ten Lectures on Wavelets. CBMS-NSF conference series in applied mathematics. SIAM Ed, 1992.

[2] Mallat, S. “A theory for multiresolution signal decomposition: the wavelet representation,” IEEE Pattern Anal. and Machine Intell., vol. 11, no. 7, 1989, pp. 674–693.

Introduced before R2006a

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