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<DIV><FONT face=Arial size=2>Hi Zach,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>a quick look at your data suggests that you have
simply run into a fundamental characteristc of measuring phase angle.
Phase angle is a continuous and repeating value. Hence, a static,
unchanging, reference point is needed. There is probably a simple tweak
you can make to your algorithm that can 'fix' your issue. Alternatively,
there are some transformations you can make:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>See:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><A
href="http://en.wikipedia.org/wiki/Quaternion">http://en.wikipedia.org/wiki/Quaternion</A></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I also came across some information about
calculating 'circular means' from circular statistics. I haven't had a
chance to check this out, but you might find it helpful. I think this was
posted on the EEGLab group a while back.</FONT></DIV><FONT face=Arial size=2><A
href="http://www.mathworks.com/matlabcentral/fileexchange/10676-circular-statistics-toolbox-directional-statistics">http://www.mathworks.com/matlabcentral/fileexchange/10676-circular-statistics-toolbox-directional-statistics</A></FONT>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Regards,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Phil</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV>
<DIV><FONT face=Arial size=2>=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=<BR>Philip Michael
Zeman B.Eng, Ph.D.<BR>Applied Brain and Vision Sciences Inc.<BR>Brain Function
Analysis for Novel Paradigms and Serious Games<BR>Analysis of Pharmaceutical
Effects on Brain Function<BR><A
href="mhtml:{439FBB32-AAF8-4DEF-9E59-73E2AD717E82}mid://00000413/!x-usc:http://www.abvsciences.com/">http://www.abvsciences.com</A><BR>Latest
Brain Research Result:<BR><A
href="mhtml:{439FBB32-AAF8-4DEF-9E59-73E2AD717E82}mid://00000413/!x-usc:http://www.spatialbrain.com/">http://www.spatialbrain.com</A><BR>Email:
<A
href="mhtml:{439FBB32-AAF8-4DEF-9E59-73E2AD717E82}mid://00000413/!x-usc:mailto:pzeman@alumni.uvic.ca">pzeman@alumni.uvic.ca</A><BR>Phone:
+1-250-589-4234<BR>LinkedIn Profile: <A
href="mhtml:{439FBB32-AAF8-4DEF-9E59-73E2AD717E82}mid://00000413/!x-usc:http://ca.linkedin.com/in/philipmichaelzeman">http://ca.linkedin.com/in/philipmichaelzeman</A><BR>=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=</FONT></DIV></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=zdmoran@gmail.com href="mailto:zdmoran@gmail.com">Zachary Moran</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=eeglablist@sccn.ucsd.edu
href="mailto:eeglablist@sccn.ucsd.edu">eeglablist@sccn.ucsd.edu</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Wednesday, April 14, 2010 11:17
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [Eeglablist] Wrapped Phase Angle
from newtimef?</DIV>
<DIV><BR></DIV>Hi Everyone,<BR><BR>I'm currently investigating the
relationship between phase angle and other EEG variables. In order to
get phase angle, I've been taking the angle(ITC) in Matlab which gives me
phase angle estimates from -pi to pi radians. However, when I plot this
data against time I find discontinuities at pi and -pi (see attached jpeg for
an example), which has become problematic in using it as a predictor
variable. <BR><BR>Does this suggest that the phase information is
"wrapped", and, if so, does Matlab's "unwrap(phase_angle_data)" function seem
appropriate to anyone else as a means of making my phase angle data better
suited as a predictor? Alternatively, I had initially wanted to
constrain phase to between 0 and 2pi radians - does anyone have any advice for
how to make this conversion? Any thoughts or ideas would be very greatly
appreciated.<BR><BR>Many thanks!<BR><BR>Zach<BR>
<P>
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