www.pudn.com > TimeFrequency.rar > WindowFT.m

function specgm = WindowFT(sig,w,m,Name,titl) 
% WindowFT -- Window Fourier Transform 
%  Usage 
%    specgm = WindowFT(sig,w,m,Name,titl) 
%  Inputs 
%    sig      1-d signal 
%    w        window half-length, default = n/2 
%    m        inter-window spacing, default=1 
%    Name     string: 'Rectangle', 'Hanning', 'Hamming', 
%             'Gaussian', 'Blackman'; Default is 'Rectangle' 
%    titl     Optional Title String Modifier 
%  Outputs 
%    specgm   Window Fourier Transform of sig, n+1 by n complex matrix 
%  Side Effects 
%    Image Plot of the Window Fourier Transform 
%  Description 
%  Algorithm 
%     supposes signal is non-periodic, i.e. zero-padded 
%  Example 
%    sig = ReadSignal('Caruso'); 
%    sig = sig(1:128); 
%    specgm = WindowFT(sig); 
%  See Also 
%    MakeWindow IWindowFT 
%  References 
%    Mallat, "A Wavelet Tour in Signal Processing";  
%            4.2.3 Discrete Windowed Fourier Transform. 
% 
	sig = sig(:); 
	n = length(sig); 
	f = [zeros(n,1); sig; zeros(n,1)]; 
% Default parameters, 
	if nargin < 2, 
		w = n/2; 
	end; 
	if nargin < 3, 
		m=1; 
	end; 
	if nargin < 4, 
		Name = 'Rectangle'; 
	end; 
	if nargin < 5, 
		titl = []; 
	end; 
% Initialize output matrix, 
	nw     = floor(n ./ m); 
	specgm = zeros(n,nw); 
	ix     = ((-w):w); 
	win    = MakeWindow(Name,w); 
	win    = win(:); 
% Computing Window Fourier Transform 
	for l=1:nw, 
	        totseg = zeros(1,3*n); 
		t = 1+ (l-1)*m; 
		tim = n + t + ix; 
		seg = f(tim); 
		seg = seg.*win; 
 
		totseg(tim) = seg; 
 
		localspec = fft(totseg(n+1:2*n)); 
		 specgm(:,l)  = localspec(1:n)'; 
%window = rshift(window')'; 
end 
% 
% Make Window Fourier Transform Display 
 	specgmShow = abs(specgm(1:(n/2+1),:)); 
	spmax = max(max(specgmShow)); 
	spmin = min(min(specgmShow)); 
	colormap(1-gray(256)) 
	image(linspace(0,n,n),linspace(0,n/2,n/2+1),256*(specgmShow-spmin)/(spmax-spmin)); 
 
	axis('xy') 
	xlabel('') 
	ylabel('Frequency') 
 
	if nargout==0, 
		specgm = []; 
	end 
% 
% Copyright (c) 1996. Xiaoming Huo 
%  
% Modified by Maureen Clerc and Jerome Kalifa, 1997 
% clerc@cmapx.polytechnique.fr, kalifa@cmapx.polytechnique.fr 
     
     
%    
% Part of WaveLab Version 802 
% Built Sunday, October 3, 1999 8:52:27 AM 
% This is Copyrighted Material 
% For Copying permissions see COPYING.m 
% Comments? e-mail wavelab@stat.stanford.edu 
%