Wavelet Toolbox

Complex Continuous Analysis Using the Command Line

This example involves a cusp signal.

1. Load a signal.

1. From the MATLAB prompt, type

   • load cuspamax; 
     

   You now have the signal cuspamax in your workspace:

   • whos
     
     

     Name	Size	Bytes	Class
     caption	1x71	142	char array
     cuspamax	1x1024	8192	double array

      
      
     
     caption
     
     caption =
            x = linspace(0,1,1024);
            y = exp(-128*((x-0.3).^2))-3*(abs(x-0.7).^0.4);
     

   caption is a string that contains the signal definition.

2. Perform a Continuous Wavelet Transform.

1. Use the cwt command. Type

   • c = cwt(cuspamax,1:2:64,'cgau4');
     

   The arguments to cwt specify the signal to be analyzed, the scales of the analysis, and the wavelet to be used. The returned argument c contains the coefficients at various scales. In this case, c is a complex 32-by-1024 matrix, each row of which corresponds to a single scale.

3. Plot the coefficients.

1. The cwt command accepts a fourth argument. This is a flag that, when present, causes cwt to produce four plots related to the complex continuous wavelet transform coefficients:
   • Real and imaginary parts
   • Modulus and angle

   The cwt command can accept more arguments to define the different characteristics of the produced plots. For more information, see the cwt reference page.

   Type

   • c = cwt(cuspamax,1:2:64,'cgau4','plot');
     

   A plot appears:

   Of course, coefficient plots generated from the command line can be manipulated using ordinary MATLAB graphics commands.

One-Dimensional Complex Continuous Wavelet Analysis

Complex Continuous Analysis Using the Graphical Interface