<div dir="ltr">Dear Yusuf and Peter,<div><br></div><div>My experience is also that negative squared wPLI values should not be considered, as they constitute a side-effect of the debiasing technique. I would rather clip them to zero, or, better, assign them a NaN (since the result is undetermined).</div><div><br></div><div>I hope this helped.</div><div>Cris</div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Feb 19, 2016 at 3:04 PM, Prasandhya Astagiri Yusuf <span dir="ltr"><<a href="mailto:prasandhya.a.yusuf@gmail.com" target="_blank">prasandhya.a.yusuf@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"><div><div><div><div><div>Hi Peter,<br></div>sorry for the (very) late response, I guess you have already figured the answer by now. Anyhow, in case someone has similar problem, I try to share my experience here in the forum.<br><br></div>I recently computed the debiased WPLI and experienced the same problem. I also found this negative value of debiased WPLI quite frequently asked in this mailing list, even Mr. Martin Vinck himself has already responded to it on June 2011.<br></div><div>So as stated in the paper (Vinck et al. 2011), PLI and WPLI result has the range from 0 to 1. But the debiased WPLI could yields negative values as a consequence of debiasing method. One of his latest paper (Phillips, 2014), they mentioned in the Materials and Methods that "the debiased WPLI estimator (Vinck et al. 2011), ranging from zero (<u>negative values can incidentally occur because of limited sampling</u>) to one (maximum coherence)". <br>So in my opinion, we can neglect this negative values and convert them to zeros. But surely, we should not take the absolute value from it. <br></div><br></div>Best,<br></div>Sandhy<br><br><br>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Arial",sans-serif" lang="DE">Prasandhya A. Yusuf</span><span lang="DE"> </span></p>
<p class="MsoNormal"><b><span style="font-size:10pt;font-family:"Arial",sans-serif;color:black" lang="DE">Medizinische Hochschule Hannover</span></b><span lang="DE"></span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Arial",sans-serif;color:black">Experimentelle Otologie / OE 8891 / </span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Arial",sans-serif;color:black">VIANNA / M13</span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Arial",sans-serif;color:black">Feodor-Lynen-Str. 35</span><span style="font-size:10pt;font-family:"Arial",sans-serif;color:rgb(31,73,125)"> </span></p>
<p class="MsoNormal"><span style="font-size:10pt;font-family:"Arial",sans-serif;color:black">D-30625 Hannover</span></p>
<br><div><div><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Mon, Dec 21, 2015 at 8:39 PM, Peter Lyons <span dir="ltr"><<a href="mailto:plyons@udel.edu" target="_blank">plyons@udel.edu</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div dir="ltr"><div>Hello Everyone,</div><div><br></div><div>I have a question regarding the interpretation of negative values in the debiased wPLI. Although the reference page on the debiased wPLI notes that estimates are computed by squaring the wPLI values, I and others have noticed that some of the values in the debiased wPLI spectrum are negative. How should these negative values be interpreted in reference to 0?</div><div><br></div><div>To view the results of the debiased wPLI connectivity analysis (ft_connectivity analysis with cfg.method = 'wpli_debiased'), I've been using the ft_topoplotER function. However, I'm concerned that the default scaling (zlim = 'maxmin') of the plot does not seem to register the negative values in the debiased wPLI spectrum. That is, the negative values are not being plotted. It is curious, however, that the ft_topoplotER does register the negative values in the <em>non-debiased </em>wPLI spectrum. </div><div><br></div><div>Is there a reason why the ft_topoplotER function is treating the negative values from the debiased vs. non-debiased wPLI spectrums differently? Is there perhaps a more appropriate plotting function I should be using to view the debiased wPLI output?</div><div><br></div><div>I would greatly appreciate any guidance in this. </div><div><br></div><div>Thank you!</div><span><font color="#888888"><div><br></div><div>Peter</div></font></span></div>
<br></div></div>_______________________________________________<br>
fieldtrip mailing list<br>
<a href="mailto:fieldtrip@donders.ru.nl" target="_blank">fieldtrip@donders.ru.nl</a><br>
<a href="http://mailman.science.ru.nl/mailman/listinfo/fieldtrip" rel="noreferrer" target="_blank">http://mailman.science.ru.nl/mailman/listinfo/fieldtrip</a><br></blockquote></div><br></div>
<br>_______________________________________________<br>
fieldtrip mailing list<br>
<a href="mailto:fieldtrip@donders.ru.nl">fieldtrip@donders.ru.nl</a><br>
<a href="http://mailman.science.ru.nl/mailman/listinfo/fieldtrip" rel="noreferrer" target="_blank">http://mailman.science.ru.nl/mailman/listinfo/fieldtrip</a><br></blockquote></div><br></div>