Plotting continuous wavelet in 3D

Hello everybody,

I am working with wavelets since a very short time, and I have a very basic question that I am not able to figure out myselfs. In matlab the cwt command is computing the continuous wavelet transform of a sequence:

scales = (1:2^lev);
cwt(signal, scales, wname, 'plot');

when doing this, I get a nice 2D plot, but what if I would like to plot the typical 3D (time, scale, amplitude) plot of the wavelet transform? How can I obtain this?

[Gali Amoolya]

Hey,

I am also stuck up with the same problem. Could you get the solution to this after it? If yes, please help me.

Answer 1

[Raghunandan V]

Hi,

I dont know about cwt command. My idea would be to store the values obtained from cwt command in to 2 variables and then use surf command to plot it in 3d by adding another variable.

[Humberto Merizalde]

Could you please write an example.

Answer 2

[Christopher McCausland]

Hi Giovanni,

I am very late to the party, but for anyone looking a fuller answer to this, it can be found on the tfridge() documentation page, under 'Find Ridge of Noisy Signal'. The following code is lifted directly from the matlab documentation:

% Create a matrix that resembles a time-frequency matrix with a sharp ridge. 
% Visualize the matrix in three dimensions.
t = 0:0.05:10;
f = 0:0.2:8;
rv = 1;

[F,T] = ndgrid(f,t);

S = zeros(size(T));
S(abs((F-4)-cos((T-6).^2))<0.1) = rv;

mesh(T,F,S)
view(-30,60)

% Add noise to the matrix and redisplay the plot.
S = S+rand(size(S))/10;

mesh(T,F,S)
view(-30,60)
xlabel('Time')
ylabel('Frequency')

Surf, or Mesh can be use to make these types of 3d graphs, an the viewpoint set to an isometric position so you can really explain what you are doing. Looks very nice for papers.

I hope this helps,

Chrisopher