% generate signal

N=128;
sig=fmlin(N,0,0.5);
t=1:N;

% make plot

plot(t,real(sig)); 
axis([t(1) t(N) -1 1]);
xlabel('Time'); 
ylabel('Real part');
title('Linear frequency modulation'); 
grid;

% compute spectrum

dsp=fftshift(abs(fft(sig)).^2);
f=(-N/2:N/2-1)/N;

% make frequency plot

plot(f,dsp);
xlabel('Normalized frequency'); ylabel('Squared modulus');
title('Spectrum'); grid

% compute time-frequency representation
tfr=tfrwv(sig);

%% make plot
colormap(jet);
imagesc(t/fs,fs*f,flipud(tfr));

%% note: matlab users can use a GUI to adjust the layout
%% and other parameters of the display. this utility is
%% not yet available with GNU octave.