<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Using filters is always a “problem”. A symmetric filter will at least not misplace your signal of interest. My reply referred to the “weirdness at the right edge”. <div class=""><br class=""><div class="">Best</div><div class="">tzvetan</div><div class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">Am 18.06.2020 um 14:44 schrieb george michael <<a href="mailto:gmichael_@hotmail.com" class="">gmichael_@hotmail.com</a>>:</div><br class="Apple-interchange-newline"><div class=""><div style="caret-color: rgb(0, 0, 0); font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class="">Dear Tzvetan,</div><div style="caret-color: rgb(0, 0, 0); font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class=""><br class=""></div><div style="caret-color: rgb(0, 0, 0); font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class="">thanks you for the quick reply.</div><div style="caret-color: rgb(0, 0, 0); font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class="">Wouldn't be a problem to use "onepass-zerophase" or "twopass" given that I am interested in phase at stimulus onset?</div><div style="caret-color: rgb(0, 0, 0); font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class="">Don't both filter-types smear poststimulus activity into the prestimulus interval?<br class=""></div><div style="caret-color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><div id="appendonsend" class=""></div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class=""><br class=""></div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class="">Best,</div><div style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;" class="">Georgios<br class=""></div><hr tabindex="-1" style="display: inline-block; width: 2298.09375px;" class=""><div id="divRplyFwdMsg" dir="ltr" class=""><font face="Calibri, sans-serif" style="font-size: 11pt;" class=""><b class="">From:</b><span class="Apple-converted-space"> </span>fieldtrip <<a href="mailto:fieldtrip-bounces@science.ru.nl" class="">fieldtrip-bounces@science.ru.nl</a>> on behalf of Tzvetan Popov <<a href="mailto:tzvetan.popov@uni-konstanz.de" class="">tzvetan.popov@uni-konstanz.de</a>><br class=""><b class="">Sent:</b><span class="Apple-converted-space"> </span>Thursday, June 18, 2020 14:27<br class=""><b class="">To:</b><span class="Apple-converted-space"> </span>FieldTrip discussion list <<a href="mailto:fieldtrip@science.ru.nl" class="">fieldtrip@science.ru.nl</a>><br class=""><b class="">Subject:</b><span class="Apple-converted-space"> </span>Re: [FieldTrip] single-trial phase at stimulus onset using Hilbert transform</font><div class=""> </div></div><div class="" style="word-wrap: break-word; line-break: after-white-space;">Dear Georgios,<div class=""><br class=""></div><div class="">the reason is your cfg.bpfiltdir = ‘onepass’. This should be zero phase or twopass filter. Yet, you will still get filter artefacts at the edges. I suggest you should re-segment your data, e.g. -1000 to 500ms, filter and then re-segment to -500 to 0 again.</div><div class="">Good luck,</div><div class="">tzvetan</div><div class=""><br class=""></div><div class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">Am 18.06.2020 um 14:14 schrieb george michael <<a href="mailto:gmichael_@hotmail.com" class="">gmichael_@hotmail.com</a>>:</div><br class="x_Apple-interchange-newline"><div class=""><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Dear Fieldtrip Community,</div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"><br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">I am trying to extract the alpha phase at stimulus onset from single trials.<span class="x_Apple-converted-space"> </span><br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">My approach is to :<br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">1) Band-pass filter the trial segments from -500ms to 0 (<span class="">±</span>1Hz around individual alpha frequency).</div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">I use the filter 'firws' and filter direction 'onepass' to avoid smearing poststimulus activity into the prestimulus interval.<span class="" style="left: 612.92px; top: 156.986px; font-size: 16.4px; font-family: sans-serif;"></span><br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">2) Compute Hilbert transform to extract the instantaneous phase of the bandpass signal.<span class="x_Apple-converted-space"> </span><br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">3) Select the phase at the last sample (t=0) as the one representing phase at stimulus onset.</div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"><br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"><span class=""> cfg=[];<br class=""></span></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"><span class="">cfg.channel = 'O1';<br class=""></span><div class="">cfg.bpfilter='yes';<br class=""></div><div class="">cfg.bpfreq=[foi-1 foi+1];<br class=""></div><div class="">cfg.bpfilttype= 'firws';<br class=""></div><div class="">cfg.bpfiltdir= 'onepass';</div><div class="">cfg.hilbert='angle';</div><div class="">phase = ft_preprocessing(cfg , trials_prestim);</div></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"><br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"><span class=""> for tr=1:length(phase .trial)</span><br class=""><span class=""></span><div class=""> phase_onset(tr,:)=<span class="">phase<span class="x_Apple-converted-space"> </span></span>.trial{tr}(:,end); % select phase at last sample<br class=""></div><span class=""> end</span></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"><span class=""></span><br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">The problem is that the band-bass signal looks quite weird at the right edge, towards t=0s (see attached figure). </div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"><br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Do you have any idea what would be the reason for this problem?<span class="x_Apple-converted-space"> </span><br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">And which would be the optimal way to extract phase at stimulus onset?</div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"> <br class=""></div><div class="" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none;">Many thanks,<br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Georgios</div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">-----------------------</div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Georgios Michail, MSc.</div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Department of Psychiatry and Psychotherapy</div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;">Charite-Universitätsmedizin Berlin<br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"><br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"><br class=""></div><div class="" style="font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; text-decoration: none; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt;"><br class=""></div><span id="x_cid:CD0CE12F-5A7D-457E-BDE1-8E2D4C11F836@fritz.box" class=""><bandpass_alpha_singlesubj.png></span><span class="" style="font-family: Helvetica; font-size: 12px; 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