?? maxfilt.m
字號:
function [y,k,y0]=maxfilt(x,f,n,d,x0)
%MAXFILT find max of an exponentially weighted sliding window [Y,K,Y0]=(X,F,N,D,X0)
%
% Inputs: X Vector or matrix of input data
% F exponential forgetting factor in the range 0 (very forgetful) to 1 (no forgetting)
% F=exp(-1/T) gives a time constant of T samples
% N Length of sliding window [default = size(X,D)]
% D Dimension for work along [default = first non-singleton dimension]
% X0 Initial values placed in front of the X data
%
% Outputs: Y Output matrix - same size as X
% K Index array: Y=X(K). (Note that these value may be <=0 if input X0 is present)
% Y0 Last N-1 values (used to initialize a subsequent call to maxfilt())
%
% This routine calaulates y(p)=max(f^r*x(p-r), r=0:n-1) where x(r)=-inf for r<1
% y=x(k) on output
% Example: find all peaks in x that are not exceeded within +-w samples
% w=4;m=100;x=rand(m,1);[y,k]=maxfilt(x,1,2*w+1);p=find(((1:m)-k)==w);plot(1:m,x,'-',p-w,x(p-w),'+')
% Copyright (C) Mike Brookes 2003
% Version: $Id: maxfilt.m,v 1.7 2008/06/02 08:11:45 dmb Exp $
%
% VOICEBOX is a MATLAB toolbox for speech processing.
% Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% This program is free software; you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation; either version 2 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You can obtain a copy of the GNU General Public License from
% http://www.gnu.org/copyleft/gpl.html or by writing to
% Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if nargin>4 % initial values specified
y=shiftdim(cat(d,x0,x),d-1); % concatenate x0 and x along d
nx0=size(x0,d);
elseif nargin<4
[y,d]=shiftdim(x); % no dimension specified
nx0=0;
else
y=shiftdim(x,d-1); % dimension specified
nx0=0;
end
s=size(y);
l=s(1);
if nargin<3
n=l;
end
if nargout>2
ny0=min(l,n-1);
sy0=s;
sy0(1)=ny0;
y0=reshape(y(1+l-ny0:end,:),sy0);
if nargin<4
y0=shiftdim(y0,-d);
else
y0=shiftdim(y0,ndims(x)-d+1);
end
end
n=min(n,l); % no point in having n>l
k=repmat((1:l)',[1 s(2:end)]);
j=1;
j2=1;
while j>0
g=f^j;
m=find(y(j+1:l,:)<=g*y(1:l-j,:));
m=m+j*fix((m-1)/(l-j));
y(m+j)=g*y(m);
k(m+j)=k(m);
j2=j2+j;
j=min(j2,n-j2);
end
if nargout==0
if nargin<3
x=shiftdim(x);
else
x=shiftdim(x,d-1);
end
ss=prod(s(2:end));
plot(1:l,reshape(y(nx0+1:end,:),l,ss),'r',1:l,reshape(x,l,ss),'b');
else
if nargin<4
y=shiftdim(y,-d);
k=shiftdim(k,-d);
elseif nargin>4
s(1)=s(1)-nx0;
y=shiftdim(reshape(y(nx0+1:end,:),s),ndims(x)-d+1);
k=shiftdim(reshape(k(nx0+1:end,:),s),ndims(x)-d+1)-nx0;
else
y=shiftdim(y,ndims(x)-d+1);
k=shiftdim(k,ndims(x)-d+1);
end
end
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