function w = fswindow(N,wt,a)%FSWINDOW Generate Window Functions.% FSWINDOW(N,TYPE) creates a window vector of type TYPE having% a length equal to the scalar N.% FSWINDOW(X,TYPE) creates a window vector of type TYPE having% a length and orientation the same as the vector X.% FSWINDOW(.,TYPE,alpha) provides a parameter alpha as required% for some window types.% FSWINDOW with no input arguments returns a string matrix whose% i-th row is the i-th TYPE given below.%% TYPE is a string designating the window type desired:% 'rec' = Rectangular or Boxcar% 'tri' = Triangular or Bartlet% 'han' = Hann or Hanning% 'ham' = Hamming% 'bla' = Blackman common coefs.% 'blx' = Blackman exact coefs.% 'rie' = Riemann {sin(x)/x}% 'tuk' = Tukey,  0< alpha < 1; alpha = 0.5 is default% 'poi' = Poisson, 0< alpha < inf; alpha = 1 is default% 'cau' = Cauchy, 1< alpha < inf; alpha = 1 is default% 'gau' = Gaussian, 1< alpha < inf; alpha = 1 is default%% Reference: F.J. Harris,"On the Use of Windows for Harmonic Analysis with the% Discrete Fourier Transform," IEEE Proc., vol 66, no 1, Jan 1978, pp 51-83.% D.C. Hanselman, University of Maine, Orono, ME  04469% 1/10/95% Copyright (c) 1996 by Prentice-Hall, Inc. if nargin==0	w=['rec';'tri';'han';'ham';'bla';'blx';'rie';'tuk';'poi';'cau';'gau'];	returnend[r,c]=size(N);n=max(r,c);if n>1,N=n;endwt=[wt(:)' '   '];wt=wt(1:3);if strcmp(wt,'rec')				% rectangular	w = ones(1,N);elseif strcmp(wt,'tri')			% triangular	m=(N-1)/2;	w=(0:m)/m;	w=[w w(ceil(m):-1:1)];elseif strcmp(wt,'han')			% hanning	m=linspace(-pi,pi,N);	w=0.5*(1 + cos(m));elseif strcmp(wt,'ham')			% hamming	m=linspace(-pi,pi,N);	w=.54 + .46*cos(m);elseif strcmp(wt,'bla')			% blackman	m=linspace(-pi,pi,N);	w=.42 +.5*cos(m) + .08*cos(2*m);elseif strcmp(wt,'blx')			% blackman exact	m=linspace(-pi,pi,N);	w=(7938 + 9240*cos(m) + 1430*cos(2*m))/18608;elseif strcmp(wt,'rie')			% riemann	m=linspace(-pi,pi,N)+eps;	w=sin(m)./(m);elseif strcmp(wt,'tuk')			% tukey	if nargin<3,a=0.5;end	m=fix((a+1)*N/2);	w=ones(1,N);	if a>0&a<1		w(m:N)=0.5*(1 + cos(pi*((m:N)-m)/(N-m)));		w(1:N-m+1)=w(N:-1:m);	endelseif strcmp(wt,'poi')			% poisson	if nargin<3,a=1;end	m=round(N/2)-1;	w=[(m:-1:0) (rem(N,2):m)]/m;	w=exp(-abs(a)*w);elseif strcmp(wt,'cau')			% cauchy	if nargin<3,a=1;end	m=round(N/2)-1;	w=[(m:-1:0) (rem(N,2):m)]/m;	w=(1+(a*w).^2).^(-1);elseif strcmp(wt,'gau')			% gaussian	if nargin<3,a=1;end	m=round(N/2)-1;	w=[(m:-1:0) (rem(N,2):m)]/m;	w=exp(-0.5*(a*w).^2);else	error('Incorrect Window type requested');endif r>1,w=w.';end