[Fwd: freqanalysis_wltconvol.m wavelets]

Brian Roach brian.roach at YALE.EDU
Thu May 22 22:14:01 CEST 2008

-------- Original Message --------
Subject: 	freqanalysis_wltconvol.m wavelets
Date: 	Thu, 22 May 2008 12:47:11 -0700
From: 	Brian Roach <brian.roach at ncire.org>
To: 	FieldTrip discussion list <FIELDTRIP at NIC.SURFNET.NL>

Hi All,

Attached is a plot with 6 iterations of freqanalysis_wltconvol.m run
(40Hz wavelet plotted).  From top to bottom, these plots show

1. cfg.width = 7, cfg.gwidth = 1
2. cfg.width = 7, cfg.gwidth = 2
3. cfg.width = 7, cfg.gwidth = 3
4. cfg.width = 14, cfg.gwidth = 4
5. cfg.width = 14, cfg.gwidth = 5
6. cfg.width = 14, cfg.gwidth = 6

My question is regarding the peaks of the windowed wavelets - why are
they offset from one another?  I would think that the peak latencies
should not shift, only the number of cycles or the length of the gauss
should change with the cfg manipulations above.

In addition to that question, I have attached a screen shot from the
matlab help on the topic of complex morlet wavelets.  There, it looks
like the real part should have its peak at the 0 point or middle of the
gauss, which does not appear to be the case in any of my 6 examples.  Is
this peak at 0ms a necessary feature or a morlet wavelet, or is it
always plotted this way as a convention, not as a rule?

thank you,

The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/fcdonders/fieldtrip.
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