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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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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');

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`.

HTH

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 vonkoch=vonkoch(1:510); 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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