<div dir="ltr"><div>Thanks for the discussion, I am using TFCE myself and it is helpful to see what others think about it. It seems safest to me to always start at 0 and increase the step size to ease computational burden, as changing the start value seems much more likely to have drastic effects on the overall result than changing the step size. </div><div><br></div>Also, sorry to be a bit pedantic, but while I completely understand wanting to play with the method to see how the parameters might affect the results, please keep in mind that going back and changing the start/step values to get different (or possibly 'more significant') p-values is problematic. To me, one of the main benefits of using TFCE is to avoid having to choose a single threshold ahead of time, as trying several thresholds and picking the 'best one' results in a new multiple comparisons issue that is typically not accounted for. <div><div><br><div><br></div><div><br></div></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Jul 18, 2016 at 3:49 PM, Cushing, Cody <span dir="ltr"><<a href="mailto:CCUSHING1@mgh.harvard.edu" target="_blank">CCUSHING1@mgh.harvard.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div style="direction:ltr;font-family:Tahoma;color:#000000;font-size:10pt">Ah, alright beautiful. Thanks for the explanation Eric. I'm imagining using a start of 2 on a whole brain analysis would not make much of a difference, which I'm imagining is
where that number was coming from. <br>
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Cheers,<br>
Cody<br>
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<div style="direction:ltr"><font face="Tahoma" color="#000000" size="2"><span class=""><b>From:</b> <a href="mailto:mne_analysis-bounces@nmr.mgh.harvard.edu" target="_blank">mne_analysis-bounces@nmr.mgh.harvard.edu</a> [<a href="mailto:mne_analysis-bounces@nmr.mgh.harvard.edu" target="_blank">mne_analysis-bounces@nmr.mgh.harvard.edu</a>] on behalf of Eric Larson [<a href="mailto:larson.eric.d@gmail.com" target="_blank">larson.eric.d@gmail.com</a>]<br>
</span><b>Sent:</b> Monday, July 18, 2016 3:38 PM<span class=""><br>
<b>To:</b> Discussion and support forum for the users of MNE Software<br>
<b>Subject:</b> Re: [Mne_analysis] TFCE parameters<br>
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<div style="direction:ltr;font-family:Tahoma;color:#000000;font-size:10pt">Is there any motivation behind start>0 other than trying to reduce computation time?</div>
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<div>Not as far as I know.</div>
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<div style="direction:ltr;font-family:Tahoma;color:#000000;font-size:10pt">Why are these the 2 parameters we have control for TFCE? What's to be gained/lost?<br>
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<div>Think of it as a way to approximate an integral where each function value to put into the summation takes a long time to compute (the clustering step). Ideally we would start at zero and go in infinitesimal steps to the largest statistic value, but numerically
that's infeasible and practically it would take forever. So the idea is to compute as few as possible (highest start and biggest step) without affecting the result. If using a smaller start and/or step affects the output, then you should use the smaller start
and/or step because it should provide a better approximation to the integral. Without looking back, I would assume a start of 2 was suggested because it usually doesn't affect the result (at least in the suggester's experience).</div>
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<div>Eric</div>
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