MATLAB Answers


Asked by Lisa Justin on 13 Dec 2011

how do a plot3 of a wavelet tranform showing time, scale and wavelet coefficients




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3 Answers

Answer by Wayne King
on 14 Dec 2011
 Accepted answer

Hi Lisa, To use plot3, you must have your time (position) and scale vectors as matrices because the CWT coefficients are in a matrix.

You can use meshgrid() to transform your time and scale vectors into matrices suitable for plot3()

t = 1:1024;
a = 1:30;
Wt = abs(randn(30,1024));
[T,A] = meshgrid(t,a);
plot3(T,A,Wt); xlabel('time'); 
ylabel('Scale'); zlabel('CWT magnitude');

However, I think you may find surf() better here

    surf(t,a,Wt); shading interp;
    xlabel('time'); ylabel('scale'); zlabel('CWT magnitude');

  1 Comment

Lisa Justin on 14 Dec 2011

thanks! i will try it now

Answer by Honglei Chen
on 13 Dec 2011

Hi Lisa,

I don't think plot3 is appropriate for your purpose. I think you probably better off using image or imagesc.



Answer by Wayne King
on 13 Dec 2011

Hi Lisa, If I remember correctly you are using your own CWT algorithm, not MATLAB's cwt() or cwtft(). Is that correct? Are you coefficients in a matrix scale-position? I think you want surf

load vonkoch
len = length(vonkoch);
cw1 = cwt(vonkoch,1:32,'sym2','plot'); 
% cw1 is 32x510
surf(1:510,1:32,cw1); shading interp;
xlabel('Position'); ylabel('Scale'); zlabel('CWT Coefficients');
colormap jet;
view([-27 42]);

Keep in mind that if you are using a complex-valued analyzing wavelet, you will have to input the moduli (abs()), or the real or imaginary parts.


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