mywindow.m

matlab源代码

function h=mywindow(N,name,param,param2)
%	h=mywindow(n,name,param,param2)
%	yields a window of length N with a given shape.
%
%	n      : length of the window
%	name   : name of the window shape (default : hamming)
%	param  : optional parameter
%	param2 : second optional parameters
%
%	Possible names are :
%       'Bartlett', 'Blackman', 'Dolph'
%       'Gauss',    'Hamming',  'Hanning', 'none'
%       'Parzen',   'Papoulis', 'rect',    'triang'
%	'Hamming', 'Hanning', 'Harris', 'Papoulis'
%
%	For the gaussian window, an optionnal parameter K
%	sets the value at both extremities. The default value is 0.005
%
%	Example : h=mywindow(256,'Gauss',0.005);
%                 plot(h);
%

if nargin==0
   error ('At least 1 parameter is required')
end

if N <= 0
   error('N should be strictly positive.')
end;

if (nargin==1)
   name= 'Hamming';
end ;
name=upper(name);

if strcmpi(name,'Fejer')
   nh=fix(N/2);
   ind=(1:nh-1)/nh;
   h1=sin(pi*ind*(nh+1)).^2./(sin(pi*ind).^2*(nh+1));
   h=h1;
%  h= needs checking
elseif strcmp(name,'RECTANG') | strcmp(name,'RECT') | strcmp(name,'NONE'), 
   h=ones(N,1);

elseif strcmp(name,'HAMMING'),
   h=0.54 - 0.46*cos(2.0*pi*(1:N)'/(N+1));

elseif strcmp(name,'HANNING') | strcmp(name,'HANN'),
  h=0.50 - 0.50*cos(2.0*pi*(1:N)'/(N+1));

elseif strcmp(name,'KAISER'),
  if (nargin==3)
     beta=param; 
  else 
     beta=3.0*pi; 
  end;
  ind=(-(N-1)/2:(N-1)/2)' *2/N;
  h=bessel(0,j*beta*sqrt(1.0-ind.^2))/real(bessel(0,j*beta));

elseif strcmp(name,'NUTTALL'),
 ind=(-(N-1)/2:(N-1)/2)' *2.0*pi/N;
 h=+0.3635819 ...
   +0.4891775*cos(    ind) ...
   +0.1363995*cos(2.0*ind) ...
   +0.0106411*cos(3.0*ind) ;

elseif strcmp(name,'BLACKMAN'),
   ind=(-(N-1)/2:(N-1)/2)' *2.0*pi/N;
   h=0.42 + 0.50*cos(ind) + 0.08*cos(2.0*ind);

elseif strcmp(name,'HARRIS'),
   ind=(1:N)' *2.0*pi/(N+1);
   h=+0.35875 ...
     -0.48829 *cos(    ind) ...
     +0.14128 *cos(2.0*ind) ...
     -0.01168 *cos(3.0*ind);

elseif strcmp(name,'BARTLETT') | strcmp(name,'TRIANG'),
   h=2.0*min((1:N),(N:-1:1))'/(N+1);

elseif strcmp(name,'BARTHANN'),
   h=0.38 * (1.0-cos(2.0*pi*(1:N)/(N+1))') ...
   + 0.48 * min((1:N),(N:-1:1))'/(N+1);

elseif strcmp(name,'PAPOULIS'),
   ind=(1:N)'*pi/(N+1); 
   h=sin(ind);

elseif strcmp(name,'GAUSS'),
   if (nargin==3)
      K=param; 
   else 
      K=0.005; 
   end;
   h= exp(log(K) * linspace(-1,1,N)'.^2 );

elseif strcmp(name,'PARZEN'),
   ind=abs(-(N-1)/2:(N-1)/2)'*2/N; 
   temp=2*(1.0-ind).^3;
   h=min(temp-(1-2.0*ind).^3,temp);

elseif strcmp(name,'HANNA'),
   if (nargin==3)
      L=param; 
   else 
      L=1; 
   end;
   ind=(0:N-1)';
   h=sin((2*ind+1)*pi/(2*N)).^(2*L);

elseif strcmp(name,'DOLPH') | strcmp(name,'DOLF'),
   if (rem(N,2)==0)
      oddN=1; 
      N=2*N+1; 
   else 
      oddN=0; 
   end;
   if nargin==3
      A=10^(param/20); 
   else 
      A=1e-3; 
   end;
   K=N-1; 
   Z0=cosh(acosh(1.0/A)/K); 
   x0=acos(1/Z0)/pi; 
   x=(0:K)/N; 
   indices1=find((x<x0)|(x>1-x0));
   indices2=find((x>=x0)&(x<=1-x0));
   h(indices1)= cosh(K*acosh(Z0*cos(pi*x(indices1))));
   h(indices2)= cos(K*acos(Z0*cos(pi*x(indices2))));
   h=fftshift(real(ifft(A*real(h))));h=h'/h(K/2+1);
   if oddN
      h=h(2:2:K); 
   end;

   elseif strcmp(name,'NUTBESS'),
      if nargin==3
         beta=param; nu=0.5; 
      elseif nargin==4
         beta=param; nu=param2;
     else 
        beta=3*pi; 
        nu=0.5;
     end;
     ind=(-(N-1)/2:(N-1)/2)' *2/N; 
     h=sqrt(1-ind.^2).^nu .* ...
     real(bessel(nu,j*beta*sqrt(1.0-ind.^2)))/real(bessel(nu,j*beta));

     elseif strcmp(name,'SPLINE'),
     if (nargin < 3),
        error('Three or four parameters required for spline windows');
     elseif (nargin==3),
        nfreq=param; p=pi*N*nfreq/10.0;
     else 
        nfreq=param; p=param2;
     end;
     ind=(-(N-1)/2:(N-1)/2)'; 
     h=sinc((0.5*nfreq/p)*ind) .^ p;

else 
   error([' Unknown window: ',name]);

end