Wavelet Toolbox™

Scalogram for continuous wavelet transform

Syntax

• SC = wscalogram(TYPEPLOT,COEFS)
  SC = wscalogram(TYPEPLOT,COEFS,'PropName1',PropVal1,...)
  

Description

SC = wscalogram(TYPEPLOT,COEFS) computes the scalogram SC which represents the percentage of energy for each coefficient. COEFS is the matrix of the continuous wavelet coefficients (see cwt).

The scalogram is obtained by computing:

• S = abs(coefs.*coefs); SC = 100*S./sum(S(:))
  

When TYPEPLOT is equal to 'image', a scaled image of scalogram is displayed. When TYPEPLOT is equal to 'contour', a contour representation of scalogram is displayed. Otherwise, the scalogram is returned without plot representation.

SC = wscalogram(TYPEPLOT,COEFS,'PropName1',PropVal1,...) allows you to modify some properties. The valid choices for PropName are:

'scales'	Scales used for the CWT.
'ydata'	Signal used for the CWT.
'xdata'	x values corresponding to the signal values.
'power'	Positive real value. Default value is zero.

If power > 0, coefficients are first normalized

• coefs(k,:) = coefs(k,:)/(scales(k)^power)
  

and then the scalogram is computed as explained above.

Examples

• % Compute signal s
  t = linspace(-1,1,512);
  s = 1-abs(t);
  
  % Plot signal s
  figure;
  plot(s), axis tight
  
  % Compute coefficients COEFS using cwt
  COEFS = cwt(s,1:32,'cgau4');
  
  % Compute and plot the scalogram (image option)
  figure;
  SC = wscalogram('image',COEFS);
  
  % Compute and plot the scalogram (contour option)
  figure;
  SC = wscalogram('contour',COEFS);
  
  

See Also

cwt

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