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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi Mona,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I guess you want to measure the fluctuation in the data.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">If for example you have your data in a channel-time-trial structure, you can get the RMS over electrodes by using the following:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">AvgChan = squeeze(sqrt(mean(data.^2, 1))); (Just change the dimension you want to calculate it over).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">You will then get a measure per time-trial point.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">If you check that against the rms(data,1) you see that you get the same answer.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I don’t know about a rms function in fieldtrip, but detrended fluctuation analysis involves RMS, so maybe you can start looking there.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I hope this helped you a bit.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Kind regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Casper<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> fieldtrip-bounces@science.ru.nl [mailto:fieldtrip-bounces@science.ru.nl]
<b>On Behalf Of </b>Wong-Barnum, Mona<br>
<b>Sent:</b> 28 June 2017 18:05<br>
<b>To:</b> FieldTrip discussion list<br>
<b>Subject:</b> [FieldTrip] RMS calculation<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hello fellow FieldTrip users: <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">We would like to do RMS calculations for our MEG & EEG data. My PI explains the calculation we need as follows:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">This is a very simple calculation. What it does is it takes an amplitude, meaning a sine wave like signal, that goes above and below the midline, and thus also has negative and positive values and converts them all to positive values and
then exhibits what is called “power.” All of the original values are squared and that leaves us with power which is essentially the “energy” of the signal. And of course instead of 603.1072 measures per second, we end up with only one measure per second to
help simply the overall signal.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I don’t see a RMS calculation in the FieldTrip software but there appears to be a Matlab rms function (<a href="http://www.mathworks.com/help/signal/ref/rms.html">http://www.mathworks.com/help/signal/ref/rms.html</a>).<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I’m hoping someone more knowledgeable than I can either point to an appropriate function in the FieldTrip software or confirm that the Matlab rms function will do what we are looking for?<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Mona<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Helvetica","sans-serif";color:black">*********************************************<br>
Mona Wong<br>
Web & Mobile Application Developer<br>
San Diego Supercomputer Center<br>
<br>
"Whether you think you can or you<br>
you can't, you're right."<br>
--- Henry Ford<br>
*********************************************<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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