<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"><div style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt; "><br></div><div style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt; ">Dear Chang <br></div><div style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt; ">I suggest to re-reference your data to the averaged-reference for the reasons you describe. Especially, you recorded brain activity with a high number of electrodes and the averaged-reference is more recommended</div><div style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt; ">compared to a lower number of sensors. I suggest to adopt zscore to your analysis.</div><div style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt; "><br></div><div style="font-family: 'times new
roman', 'new york', times, serif; font-size: 12pt; ">If you want to find extreme channels that differ compared to the rest regarding their amplitudes (mVolt), you can use t<span style="font-family: 'Times New Roman', serif; font-size: 12pt; background-color: white; ">he last output of
the princomp function,t2, is Hotelling'sT</span><sup style="font-family: 'Times New Roman', serif; background-color: white; ">2</sup><span style="font-family: 'Times New Roman', serif; font-size: 12pt; background-color: white; ">, a statistical
measure of the multivariate distance of each observation from the center of the
data set. This is an analytical way to find the most extreme points in the
data.</span></div><div>
<div class="MsoNormal" style="margin-top: 6pt; margin-right: 0in; margin-bottom: 4.2pt; margin-left: 24pt; background-image: initial; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: white; background-position: initial initial; background-repeat: initial initial; "><span style="font-size: 12pt; font-family: 'Times New Roman', serif; ">[st2, index] =
sort(t2,'descend'); % Sort in descending order.<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-top: 6pt; margin-right: 0in; margin-bottom: 4.2pt; margin-left: 24pt; background-image: initial; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: white; background-position: initial initial; background-repeat: initial initial; "><span style="font-size: 12pt; font-family: 'Times New Roman', serif; ">extreme = index(1)<o:p></o:p></span></div><div class="MsoNormal" style="margin-top: 6pt; margin-right: 0in; margin-bottom: 4.2pt; margin-left: 24pt; background-image: initial; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: white; background-position: initial initial; background-repeat: initial initial; "><span style="font-size: 12pt; font-family: 'Times New Roman', serif; "><br></span></div><div class="MsoNormal" style="margin-top: 6pt; margin-right: 0in; margin-bottom: 4.2pt; margin-left: 24pt; background-image:
initial; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: white; background-position: initial initial; background-repeat: initial initial; "><span style="font-size: 12pt; font-family: 'Times New Roman', serif; "><br></span></div><div class="MsoNormal" style="margin-top: 6pt; margin-right: 0in; margin-bottom: 4.2pt; margin-left: 24pt; background-image: initial; background-attachment: initial; background-origin: initial; background-clip: initial; background-color: white; background-position: initial initial; background-repeat: initial initial; "><span style="font-size: 12pt; font-family: 'Times New Roman', serif; "><br></span></div></div><div style="font-family: 'times new roman', 'new york', times, serif; font-size: 12pt; "><pre style="font-family: 'Courier New'; margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px;
padding-left: 0px; "><br class="Apple-interchange-newline">Best regards</pre><pre style="font-family: 'Courier New'; margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; ">Stavros Dimitriadis</pre><pre style="font-family: 'Courier New'; margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; "><a rel="nofollow" target="_blank" href="http://users.auth.gr/~stdimitr/index.html" style="color: rgb(35, 71, 134); outline-width: 0px; outline-style: initial; outline-color: initial; ">http://users.auth.gr/~stdimitr/index.html</a>
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