<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Thanks Søren,<div><br></div><div>I've been detrending before epoching - this should be less of a problem in distorting the epochs, I assume?</div><div><br></div><div>Best,</div><div>Andrew</div><div><br><div><div>On Mar 24, 2011, at 9:54 AM, Søren K. Andersen wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
<div text="#000000" bgcolor="#ffffff">
Hi Andrew and Baris,<br>
<br>
if you only want to remove DC-offset, subtracting the mean of each
epoch is the best:<br>
<br>
EEG.data=EEG.data-repmat(mean(EEG.data,2),[1 EEG.pnts 1]);<br>
<br>
Detrending also removes linear drifts. This is often a good idea for
time-frequency analysis. However, detrending can cause major
distortions when analyzing ERPs, especially if epochs are short!<br>
<br>
Best,<br>
Søren<br>
<br>
<br>
On 23-Mar-11 5:35 PM, Andrew Hill wrote:
<blockquote cite="mid:B1510131-E761-4969-9A17-7DE5A9A8D098@ucla.edu" type="cite">Hi Baris,
<div><br>
</div>
<div>I'm not 100% sure what you are asking, but I use "detrend" to
eliminate drift that's left in my DC recorded BDF files even
after I convert them to EDF.</div>
<div><br>
</div>
<div>e.g.:</div>
<div><br>
</div>
<div><span class="Apple-style-span" style="font-family: Arial;">EEG.data
= detrend(EEG.data);</span></div>
<div><span class="Apple-style-span" style="font-family: Arial;"><br>
</span></div>
<div><span class="Apple-style-span" style="font-family: Arial;">Best,</span></div>
<div><span class="Apple-style-span" style="font-family: Arial;">Andrew</span></div>
<div><span class="Apple-style-span" style="font-family: Arial;"><br>
</span></div>
<div>
<div>
<div>On Mar 21, 2011, at 4:50 AM, Baris Demiral wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">Hi everyone,
<div><br>
</div>
<div>Do you know which function is the "Remove DC offset" in
the Display call for?</div>
<div><br>
</div>
<div>I was not able to track it out.</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Baris<br clear="all">
<br>
-- <br>
SB Demiral, PhD.<br>
Department of Psychology <br>
7 George Square<br>
The University of Edinburgh<br>
Edinburgh, EH8 9JZ<br>
UK<br>
Phone: +44 (0131) 6503063<br>
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<pre class="moz-signature" cols="72">--
Søren K. Andersen, Ph.D.
Department of Neurosciences
University of California San Diego
La Jolla, CA 92093
Phone:(858) 534-1389
Fax: (858) 534-1566
Email: <a class="moz-txt-link-abbreviated" href="mailto:skandersen@ucsd.edu">skandersen@ucsd.edu</a></pre>
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