% script to generate 3D plot of an analytic signal

clc, clear, close all

% read a speech signal
[y,fs] = wavread('0zk_clean.wav');

% select a section of the signal
% (about 300 ms section containing a vowel in this case, because give the
% pretties picture)
y = y(0.7*fs:fs);

% let's upsample the signal 10 times for a smoother plot
y = resample(y,10,1);
fs = fs * 10;

% find the analytic signal using the hilbert transform
yh = hilbert(y);

% generate a time vector
t = ((1:length(yh))-1)/fs;

% plot the real and imaginary parts of y1h versus time in a 3d plot
figure(1)
plot3(t,real(yh),imag(yh))
grid on
axis tight

% you can select a more interesting viewpoint with the
% Figure's "Rotate 3D" button


% FANCY VERSION:
fprintf(1,'Plotting figure 2, please wait...\n');
[y,fs] = wavread('0zk_clean.wav');
y = y(0.7*fs:fs);
yh = hilbert(y);
t = ((1:length(yh))-1)/fs;
uc = exp(1j*linspace(0,2*pi,100));
H = length(uc);
yy = real(uc)' * abs(yh)';
zz = imag(uc)' * abs(yh)';
figure(2)
h = surf(repmat(t,H,1),yy,zz,repmat(abs(yh)',H,1));
set(h,'facelight','phong','facealpha',0.1,'edgecolor','none');
view(-18,36);
grid on
fprintf(1,'Done\n');