<div dir="ltr">Dear Roxanne,<div><br></div><div>I've also seen another post related to the same issue; potential scale confusion in single-trial analysis. Could you kindly post the question to EEGLAB bugzilla?</div><div><a href="https://sccn.ucsd.edu/bugzilla/enter_bug.cgi">https://sccn.ucsd.edu/bugzilla/enter_bug.cgi</a><br></div><div>Sorry for inconvenience and thank you for your patience and cooperation.</div><div><br></div><div>Makoto</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Oct 6, 2015 at 4:00 AM, Roxanne Sopp <span dir="ltr"><<a href="mailto:roxannesopp@gmail.com" target="_blank">roxannesopp@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><pre style="color:rgb(0,0,0)"><font face="monospace, monospace">Dear all,</font></pre><pre style="color:rgb(0,0,0)"><font face="monospace, monospace">my question is somewhat related to this older post below:</font></pre><pre style="color:rgb(0,0,0)"><font face="monospace, monospace">I have precomputed power density in the STUDY function using the parameters 'specmode',[psd] in order to use the spectopo function. </font></pre><pre style="color:rgb(0,0,0)"><font face="monospace, monospace">Now i am facing two problems:</font></pre><pre style="color:rgb(0,0,0)"><font face="monospace, monospace">1. The plot does not seem to be scaled in dB (as stated below), from the script i gather that these must be the absolute power values in <span style="color:rgb(34,34,34)">µv²/Hz.. is that the case?</span></font></pre><pre style="color:rgb(0,0,0)"><span style="color:rgb(34,34,34)"><font face="monospace, monospace">2. When I additionally use 'logtrials','on' as paramters the power values seem to be scaled in dB however they still do not correspond to the values that i calculated in the single subject mode using the spectotopo function.</font></span></pre><pre><font face="monospace, monospace">What could be the difference? And which one is the valid calculation?</font></pre><pre><font face="monospace, monospace">Thanks a lot in advance for any hints and suggestions!</font></pre><pre><font face="monospace, monospace">Best regards,</font></pre><pre><font face="monospace, monospace">Roxanne</font></pre><p class="MsoNormal"><font face="monospace, monospace"></font></p><pre style="color:rgb(0,0,0)"><font face="monospace, monospace">______________________________________________________________________________</font></pre><pre style="color:rgb(0,0,0)"><font face="monospace, monospace">Dear Marco,
if you use no option to compute spectrum, then the units are power density (10*log(microvolt^2)/Hz) because the STUDY function uses the spectopo function. If you use 'specmode', 'fft', when you computed the spectrum then the unit is power values (10*log(microvolt^2)). These two are proportional but I agree that they should be made consistent. We have entered a bug report.
Best regards,
Arno
On Sep 19, 2011, at 6:33 AM, Marco Montalto wrote:
><i> Dear all,
</i>><i>
</i>><i> I have created a STUDY and pre-computed measures for power spectra using the default spectopo parameters ("fft"). My question is the following: the numerical values I extract using this code (example is with channel Fpz):
</i>><i>
</i>><i> [ STUDY specdata specfreqs] = std_specplot(STUDY, ALLEEG, 'channels', { 'Fpz' });
</i>><i>
</i>><i> are power values or voltage or amplitude etc.?
</i>><i>
</i>><i> If they are not power values can someone explain to me how I can extract power values as I need these to calculate ERD/ERS?
</i>><i>
</i>><i> Thanks and regards,
</i>><i> Marco</i></font></pre></div>
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