scalograms

[Robert Leach]

Hi,

I have another question.  Please excuse me if it's a dumb one.  I'm 
doing daubechies wavelet transforms and am trying to reproduce results 
in a paper to be sure I'm getting it right.  The plots of my low 
frequency extractions look right-on to what the paper has, but my 
scalograms look nothing like those in the paper.

A point on a scalogram as I understand it is the sum of the 
coefficients at a particular 'level'.  I figured out that I need to 
normalize the data, but all my plots have a spike going off the left 
side of the scalogram.  Everything else is flat.

What could I be doing wrong?

Their y axis goes from 0 to 1, but mine varies.  The one I'm looking at 
now goes from -4 to +4.  I'm not sure I understand where those numbers 
are coming from.  I'm using the same input signal as the paper.  I 
assume they somehow recalculated the y axis markings.  Do I need to 
convert my data like this?  Does that matter to my scalogram?  What 
difference does the y axis scale make if the low frequency plots look 
the same?

Here's some graphic examples:

This is my low frequency plot:

and here's the scalogram...

In the paper, they have a nice scalogram peak at 3.5 and a second 
smaller peak at 6.  Plus their y axis goes to 150.

Here's the code I'm using to calculate the scalogram:

        function [s]=makescalogram(wc)

        sqscales = log(size(wc,2)) / log(2);
        scales   = floor(sqscales);

        s = zeros(1,scales);

        startscale = 1;
        starti = 1;
        sz = size(wc,2);
        sq = wc.^2;
        for curscale=startscale:scales
             endi = 2**(curscale);
             if(endi > sz)
                  endi = sz
             end
             s(curscale) = (1/(2**curscale)) * sum(sq(starti:endi));
             starti = endi + 1;
        end


Rob

=====================================================================
= Robert W. Leach                                                   =
= Los Alamos National Lab                                           =
= Bioscience Division: Bioinformatics & Computational Biology Group =
= MS M888                                                           =
= Los Alamos, NM 87545                                              =
= address@hidden                                                 =
=====================================================================