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<div class="moz-cite-prefix">I would. Baseline correction removes
background components from the ERP but it does remove linear
offset that is part of the post-stimulus time series. In addition
to getting ride of DC, detrending also removes certain
non-stationarities and reduces the severity of edge effects. I
use it as a matter of course unless there is a compelling reason
to omit it from the analysis pipeline. <br>
<pre class="moz-signature" cols="72">
</pre>
On 12/7/14, 5:53 AM, Yun Wen wrote:<br>
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<p class="MsoNormal"><span style="color:#1F497D">Hi, Alexander.
Thank you for your help. Do you suggest that I do baseline
correction plus detrend, e,g, cfg.blc = 'yes' &
cfg.detrend = 'yes' on epoched data? <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Best,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Yun<o:p></o:p></span></p>
<div>
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style="font-size:10.5pt;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span style="color:windowtext">From:</span></b><span
style="color:windowtext">
<a class="moz-txt-link-abbreviated" href="mailto:fieldtrip-bounces@science.ru.nl">fieldtrip-bounces@science.ru.nl</a>
[<a class="moz-txt-link-freetext" href="mailto:fieldtrip-bounces@science.ru.nl">mailto:fieldtrip-bounces@science.ru.nl</a>] <b>On Behalf
Of </b>Alexander Nakhnikian<br>
<b>Sent:</b> Saturday, December 06, 2014 1:14 AM<br>
<b>To:</b> FieldTrip discussion list<br>
<b>Subject:</b> Re: [FieldTrip] about detrend<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal">It looks as though the take home message
is that in theory high pass filters remove DC but you can't
be sure how they will interact with empirical data since
there is no perfect filter in the real world. If other
people report substantial artifacts after filtering data
without removing the DC component I suggest getting rid of
it. To answer your original question, assuming you're
detrending each epoch individually it should remove the DC
component or at least reduce it substantially. <br>
<br>
I hope that helps.<br>
<br>
<br>
<br>
On 12/5/14, 6:20 PM, Yun Wen wrote:<span
style="font-size:12.0pt"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:#1F497D">Hi, Alexander
& Rodrigo. Thank you very much for your help. I
collected my data with DC recordings (BioSemi system). I
have seen some discussion on the DC offset:</span><o:p></o:p></p>
<p class="MsoNormal"><a moz-do-not-send="true"
href="http://sccn.ucsd.edu/pipermail/eeglablist/2014/008068.html">http://sccn.ucsd.edu/pipermail/eeglablist/2014/008068.html</a><o:p></o:p></p>
<p class="MsoNormal"><a moz-do-not-send="true"
href="http://sccn.ucsd.edu/pipermail/eeglablist/2008/002229.html">http://sccn.ucsd.edu/pipermail/eeglablist/2008/002229.html</a><o:p></o:p></p>
<p class="MsoNormal"><a moz-do-not-send="true"
href="http://sccn.ucsd.edu/pipermail/eeglablist/2010/003315.html">http://sccn.ucsd.edu/pipermail/eeglablist/2010/003315.html</a><o:p></o:p></p>
<p class="MsoNormal"><a moz-do-not-send="true"
href="http://erpinfo.org/erplab/erplab-documentation/manual/Filtering.html">http://erpinfo.org/erplab/erplab-documentation/manual/Filtering.html</a><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">It seems to
me that I’d better remove DC offset of continuous data
before high-pass filter. Am I right?</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Best,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Yun</span><o:p></o:p></p>
<p class="MsoNormal"><span style="color:#1F497D"> </span><o:p></o:p></p>
<div>
<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span style="color:windowtext">From:</span></b><span
style="color:windowtext"> </span><a
moz-do-not-send="true"
href="mailto:fieldtrip-bounces@science.ru.nl">fieldtrip-bounces@science.ru.nl</a><span
style="color:windowtext"> [</span><a
moz-do-not-send="true"
href="mailto:fieldtrip-bounces@science.ru.nl">mailto:fieldtrip-bounces@science.ru.nl</a><span
style="color:windowtext">] <b>On Behalf Of </b>Alexander
Nakhnikian<br>
<b>Sent:</b> Friday, December 05, 2014 10:19 PM<br>
<b>To:</b> FieldTrip discussion list<br>
<b>Subject:</b> Re: [FieldTrip] about detrend</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<div>
<p class="MsoNormal">Hello Again,<br>
<br>
I think there's an error in my response. I think removing
the linear trend should also set the mean to zero already
since the best fit line incorporates vertical offset.
Sorry about that. <br>
<br>
A<br>
<br>
<br>
<o:p></o:p></p>
<pre> <o:p></o:p></pre>
<p class="MsoNormal">On 12/5/14, 4:20 PM, Yun Wen wrote:<o:p></o:p></p>
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<p class="MsoNormal">Hi all, I want to remove DC offset
before applying the high-pass filter. I was wondering if
I can achieve that by putting cfg.detrend = 'yes' before
cfg.hpfilter = 'yes', something like:<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">cfg = []; <o:p></o:p></p>
<p class="MsoNormal">cfg.dataset = filename_raweeg;<o:p></o:p></p>
<p class="MsoNormal">cfg.detrend = 'yes'; <o:p></o:p></p>
<p class="MsoNormal">cfg.hpfilter = 'yes';<o:p></o:p></p>
<p class="MsoNormal">cfg.hpfiltord = 2; % Order of the
filter = 2.<o:p></o:p></p>
<p class="MsoNormal">cfg.hpfreq = 0.1; % High-pass cutoff at
0.1 Hz;<o:p></o:p></p>
<p class="MsoNormal">[data] = ft_preprocessing (cfg);<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Thank you in advance.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Best,<o:p></o:p></p>
<p class="MsoNormal">Yun<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<pre> <o:p></o:p></pre>
<pre> <o:p></o:p></pre>
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