wfilters (Wavelet Toolbox)

Wavelet filters.

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

Description

[Lo_D,Hi_D,Lo_R,Hi_R] = wfilters('wname') computes four filters associated with the orthogonal or biorthogonal wavelet named in the string 'wname'.

The four output filters are:

Lo_D, the decomposition low-pass filter
Hi_D, the decomposition high-pass filter
Lo_R, the reconstruction low-pass filter
Hi_R, the reconstruction high-pass filter

Available orthogonal or biorthogonal wavelet names 'wname' are:


Daubechies	`:`	`'db1' or 'haar', 'db2', ... ,'db10', ... ,'db50'`
Coiflets	`:`	`'coif1', ... , 'coif5'`
Symlets	`:`	`'sym2', ... , 'sym8'`
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'`

[F1,F2] = wfilters('wname','type') returns the following filters:


`Lo_D` and `Hi_D`	(Decomposition filters)	If '`type`' = `'d'`
`Lo_R` and `Hi_R`	(Reconstruction filters)	If '`type`' = `'r'`
`Lo_D` and `Lo_R`	(Low-pass filters)	If '`type`' = `'l'`
`Hi_D` and `Hi_R`	(High-pass filters)	If '`type`' = `'h'`

Examples

% Set wavelet name. 
    wname = 'db5';
% Compute the four filters associated with wavelet name given 
% by the input string wname. 
    [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')




% When used with two input arguments, depending on second
% argument, outputs are one row or one column of the previous
% figure. 
    % Decomposition filters (first row). 
    [Lo_D,Hi_D] = wfilters(wname,'d'); 
    % Reconstruction filters (second row). 
    [Lo_R,Hi_R] = wfilters(wname,'r'); 
    % Low-pass filters (first column). 
    [Lo_D,Lo_R] = wfilters(wname,'l'); 
    % High-pass filters (second column). 
    [Hi_D,Hi_R] = wfilters(wname,'h');