[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
## scalograms

**From**: |
Robert Leach |

**Subject**: |
scalograms |

**Date**: |
Wed, 18 Feb 2004 18:33:11 -0700 |

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 =
=====================================================================

**scalograms**,
*Robert Leach* **<=**