Question

matlab里没有wfilters函数怎么办？

Answer 1

不知道你要的是不是wavefilter函数，要是它的话新建一个函数M文件就行了，内容如下：
function [varargout] = wavefilter(wname, type)
%WAVEFILTER Create wavelet decomposition and reconstruction filters.
% [VARARGOUT] = WAVEFILTER(WNAME, TYPE) returns the decomposition
% and/or reconstruction filters used in the computation of the
% forward and inverse FWT (fast wavelet transform).
%
% EXAMPLES:
% [ld, hd, lr, hr] = wavefilter('haar') Get the low and highpass
% decomposition (ld, hd)
% and reconstruction
% (lr, hr) filters for
% wavelet 'haar'.
% [ld, hd] = wavefilter('haar','d') Get decomposition filters
% ld and hd.
% [lr, hr] = wavefilter('haar','r') Get reconstruction
% filters lr and hr.
%
% INPUTS:
% WNAME Wavelet Name
% ---------------------------------------------------------
% 'haar' or 'db1' Haar
% 'db4' 4th order Daubechies
% 'sym4' 4th order Symlets
% 'bior6.8' Cohen-Daubechies-Feauveau biorthogonal
% 'jpeg9.7' Antonini-Barlaud-Mathieu-Daubechies
%
% TYPE Filter Type
% ---------------------------------------------------------
% 'd' Decomposition filters
% 'r' Reconstruction filters
%
% See also WAVEFAST and WAVEBACK.

% Copyright 2002-2004 R. C. Gonzalez, R. E. Woods, & S. L. Eddins
% Digital Image Processing Using MATLAB, Prentice-Hall, 2004
% $Revision: 1.5 $ $Date: 2003/10/13 01:09:39 $

% Check the input and output arguments.
error(nargchk(1, 2, nargin));

if (nargin == 1 & nargout ~= 4) | (nargin == 2 & nargout ~= 2)
error('Invalid number of output arguments.');
end

if nargin == 1 & ~ischar(wname)
error('WNAME must be a string.');
end

if nargin == 2 & ~ischar(type)
error('TYPE must be a string.');
end

% Create filters for the requested wavelet.
switch lower(wname)
case {'haar', 'db1'}
ld = [1 1]/sqrt(2); hd = [-1 1]/sqrt(2);
lr = ld; hr = -hd;

case 'db4'
ld = [-1.059740178499728e-002 3.288301166698295e-002 ...
3.084138183598697e-002 -1.870348117188811e-001 ...
-2.798376941698385e-002 6.308807679295904e-001 ...
7.148465705525415e-001 2.303778133088552e-001];
t = (0:7);
hd = ld; hd(end:-1:1) = cos(pi * t) .* ld;
lr = ld; lr(end:-1:1) = ld;
hr = cos(pi * t) .* ld;

case 'sym4'
ld = [-7.576571478927333e-002 -2.963552764599851e-002 ...
4.976186676320155e-001 8.037387518059161e-001 ...
2.978577956052774e-001 -9.921954357684722e-002 ...
-1.260396726203783e-002 3.222310060404270e-002];
t = (0:7);
hd = ld; hd(end:-1:1) = cos(pi * t) .* ld;
lr = ld; lr(end:-1:1) = ld;
hr = cos(pi * t) .* ld;

case 'bior6.8'
ld = [0 1.908831736481291e-003 -1.914286129088767e-003 ...
-1.699063986760234e-002 1.193456527972926e-002 ...
4.973290349094079e-002 -7.726317316720414e-002 ...
-9.405920349573646e-002 4.207962846098268e-001 ...
8.259229974584023e-001 4.207962846098268e-001 ...
-9.405920349573646e-002 -7.726317316720414e-002 ...
4.973290349094079e-002 1.193456527972926e-002 ...
-1.699063986760234e-002 -1.914286129088767e-003 ...
1.908831736481291e-003];
hd = [0 0 0 1.442628250562444e-002 -1.446750489679015e-002 ...
-7.872200106262882e-002 4.036797903033992e-002 ...
4.178491091502746e-001 -7.589077294536542e-001 ...
4.178491091502746e-001 4.036797903033992e-002 ...
-7.872200106262882e-002 -1.446750489679015e-002 ...
1.442628250562444e-002 0 0 0 0];
t = (0:17);
lr = cos(pi * (t + 1)) .* hd;
hr = cos(pi * t) .* ld;

case 'jpeg9.7'
ld = [0 0.02674875741080976 -0.01686411844287495 ...
-0.07822326652898785 0.2668641184428723 ...
0.6029490182363579 0.2668641184428723 ...
-0.07822326652898785 -0.01686411844287495 ...
0.02674875741080976];
hd = [0 -0.09127176311424948 0.05754352622849957 ...
0.5912717631142470 -1.115087052456994 ...
0.5912717631142470 0.05754352622849957 ...
-0.09127176311424948 0 0];
t = (0:9);
lr = cos(pi * (t + 1)) .* hd;
hr = cos(pi * t) .* ld;

otherwise
error('Unrecognizable wavelet name (WNAME).');
end

% Output the requested filters.
if (nargin == 1)
varargout(1:4) = {ld, hd, lr, hr};
else
switch lower(type(1))
case 'd'
varargout = {ld, hd};
case 'r'
varargout = {lr, hr};
otherwise
error('Unrecognizable filter TYPE.');
end
end
...