function M=movcw4at(N,Np);%MOVCW4AT Four atoms rotating, analyzed by the Choi-Williams distribution.%	M=MOVCW4AT(N,Np) generates the movie frames illustrating the passage %	from the spectrogram to the WVD using different smoothing gaussian%	windows in the smoothed pseudo-WVD. %%	N : number of points of the analyzed signal%	Np : number of snapshots (default : 7)%	M : matrix of movie frames.%%	Example : %	 M=movcw4at(128); movie(M,5);%	O. Lemoine - June 1996.%	Copyright (c) 1996 by CNRS (France).%%	------------------- CONFIDENTIAL PROGRAM -------------------- %	This program can not be used without the authorization of its%	author(s). For any comment or bug report, please send e-mail to %	f.auger@ieee.org if nargin==0, error('The number of parameters must be at least one');elseif nargin==1,  Np=7;endM   = moviein(Np);rho = N/3;T   = sqrt(N);for k=1:Np, theta=(k-1)*pi/(2*(Np-1)); t1=N/2+rho*cos(theta); f1=0.5*(N/2+rho*sin(theta))/N; t2=N/2+rho*cos(theta+pi/2); f2=0.5*(N/2+rho*sin(theta+pi/2))/N; t3=N/2+rho*cos(theta+pi); f3=0.5*(N/2+rho*sin(theta+pi))/N; t4=N/2+rho*cos(theta+3*pi/2); f4=0.5*(N/2+rho*sin(theta+3*pi/2))/N; sig1=amgauss(N,t1,T).*fmconst(N,f1,round(t1));   sig2=amgauss(N,t2,T).*fmconst(N,f2,round(t2));   sig3=amgauss(N,t3,T).*fmconst(N,f3,round(t3));   sig4=amgauss(N,t4,T).*fmconst(N,f4,round(t4));   sig=sig1+sig2+sig3+sig4; [tfr,t,f]=tfrcw(sig,1:N,N,window(N/2+1),window(N+1),1); Max=max(max(tfr)); V=[0.1 0.3 0.5 0.7 0.9]*Max; contour(t,f,tfr,V);pause(.1) xlabel('Time'); ylabel('Frequency'); axis('xy') title('Choi-Williams distribution'); M(:,k) = getframe;end