<div dir="ltr"><div><div><div><div><div><div>Hi <span style="font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><font color="#000000">Kousik Sarathy and Diego,<br><br></font></span></div><span style="font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><font color="#000000">thank you for your repply and suggestions!<br>
</font></span></div><span style="font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><font color="#000000"></font></span><br></div>Thanks a lot for the Field Trip links Diego, it helps me to understand how Field Trip compute with wavelet. I thought field trip compute the wavelet the same way as cwt function in Matlab (using scales instead of frequencies). <br>
Yes, I think I need to consider the frequencies "available" from my computation and should be more aware of the spectral interpolation with vulnerable spectral leakage.<br></div>I am still trying to play around with the parameters so I can get what I want.<br>
<br></div>Cheers :)<br></div>Sandhy<br><div><div><div><br> </div></div></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Fri, Aug 22, 2014 at 1:08 PM, Lozano Soldevilla, D. (Diego) <span dir="ltr"><<a href="mailto:d.lozanosoldevilla@fcdonders.ru.nl" target="_blank">d.lozanosoldevilla@fcdonders.ru.nl</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div style="font-family:Times New Roman;font-size:12pt;color:#000000"><div>Hi Sandhy,</div><div><br></div><div>Could you please tell us a bit more info about how do you compute your TFR? Your problem sounds to me as your data length does not match the frequency you're asking:</div>
<div><br></div><div><a href="http://fieldtrip.fcdonders.nl/faq/why_does_my_output.freq_not_match_my_cfg.foi_when_using_wavelet_formerly_wltconvol_in_ft_freqanalyis" target="_blank">http://fieldtrip.fcdonders.nl/faq/why_does_my_output.freq_not_match_my_cfg.foi_when_using_wavelet_formerly_wltconvol_in_ft_freqanalyis</a></div>
<div><a href="http://fieldtrip.fcdonders.nl/faq/why_does_my_output.freq_not_match_my_cfg.foi_when_using_mtmconvol_in_ft_freqanalyis" target="_blank">http://fieldtrip.fcdonders.nl/faq/why_does_my_output.freq_not_match_my_cfg.foi_when_using_mtmconvol_in_ft_freqanalyis</a></div>
<div><br></div><div>If you want to space frequency logarithmically, I'd recommend you to change the y-axes scale to log-scale after the TFR. Alternatively, other people approach the frequency resolution modifying the wavelets. You can make a modified wavelets with different number of cycles per frequency although this approach it's more vulnerable to spectral leakage. This is because the wavelet at particular frequency wont fit an interger number of cycles :</div>
<div><br></div><div>cfg = [];</div><div>cfg.output = 'pow';</div><div>cfg.channel = 'MEG';</div><div>cfg.method = 'mtmconvol';</div><div>cfg.taper = 'hanning';</div>
<div>cfg.foi = 2:1:50; </div><div>cfg.t_ftimwin = linspace(3,37.5,size(cfg.foi,2))./cfg.foi; </div><div>cfg.toi = -0.5:0.05:1.5;</div><div>freq = ft_freqanalysis(cfg, data);</div><div><br></div><div>
I hope it helps,</div><div><br></div><div>Diego</div><br><hr style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:12pt"><blockquote style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:12pt;border-left-width:2px;border-left-style:solid;border-left-color:rgb(16,16,255);margin-left:5px;padding-left:5px">
<b>From: </b>"kousik sarathy" <<a href="mailto:sarathykousik@gmail.com" target="_blank">sarathykousik@gmail.com</a>><br><b>To: </b>"FieldTrip discussion list" <<a href="mailto:fieldtrip@science.ru.nl" target="_blank">fieldtrip@science.ru.nl</a>><br>
<b>Sent: </b>Friday, 22 August, 2014 11:13:22 AM<br><b>Subject: </b>Re: [FieldTrip] Non linear frequency steps in TFR<div><div class="h5"><br><br><div dir="ltr">Hey Sandhy,<div><br></div><div>Try,</div><div>cfg.foi = [7:30, 30:5:60, 60:10:120];</div>
<div><br></div><div>Alpha and beta in steps of 1 Hz, low gamma in steps of 5 Hz and so on.</div><div><br></div><div>Is this what you need?</div>
<div><br></div><div class="gmail_extra"><br clear="all"><div><div dir="ltr"><div><font color="#000000">--</font></div><div><font color="#000000">Regards,<br></font></div><div><span style="font-family:arial,sans-serif;font-size:13px;background-color:rgb(255,255,255)"><div style="text-align:left">
<font color="#000000">Kousik Sarathy, S</font></div></span></div><div style="text-align:left"><br></div></div></div>
<br><br><div class="gmail_quote">On Fri, Aug 22, 2014 at 11:01 AM, 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>Hi All,<br><br></div>I want to have a TFR plot that has the same portion for :<br>- alpha (7-15 Hz) <br>
- beta (15-30 Hz) <br>- low gamma (30-60 Hz) <br>- high gamma (60-120 Hz)<br><br>Since those bands have exponential frequency steps, I could only see very small part of alpha and (too) many high gamma band. Is there a way to make the cfg.foi in fieldtrip to have non linear steps? I tried to insert a exponential function: cfg.foi = 0.5*exp(0.6931*(3.8:0.02:7.9));<br>
</div>But fieldtrip seems only detect first and last number and make linear steps out of it.<br><br></div>Thank you in advance for any help and share!<br><br>Sandhy<br></div>
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</div></blockquote><span class="HOEnZb"><font color="#888888"><br><br><br><font size="3">-- </font><br><div style="color:rgb(0,0,0);font-family:'Times New Roman';font-size:12pt"><span name="x"></span>PhD Student<br>
Neuronal Oscillations Group<br>Donders Institute for Brain, Cognition and Behaviour <br>Centre for Cognitive Neuroimaging<br>Radboud University Nijmegen <br>NL-6525 EN Nijmegen<br>The Netherlands<br><a href="http://www.ru.nl/people/donders/lozano-soldevilla-d/" target="_blank">http://www.ru.nl/people/donders/lozano-soldevilla-d/</a><span name="x"></span><br>
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