<div dir="ltr">Hi Boukje,<div><br></div><div>Your question is not totally clear to me, so apologies if this is not what you mean. I gather that you want to segment your data into non-overlapping 2-sec intervals, starting at a single trigger in your data?</div><div><br></div><div>In any case, everything is possible, it just relies on understanding of the trl structure (always defined in samplenumbers) and the use of ft_preprocessing (in your case to read data and replace samples into a time-axis) and ft_redefinetrial (can be done afterwards)</div><div><br></div><div>It you only want to segment your data into non-overlapping 2-sec intervals you could do something like this:</div><div><ol><li>Use ft_preprocessing to read all your data as one long trial relative to your first trigger. For this you will need to enter a .trl field that has a single row with start, end, and offset in samplenr. You can get the sample number of your trigger (as well as the (relative) beginning and end sample numbers) using ft_read_events. The output of ft_preprocessing will give you a single trial defined in time around your trigger.<br></li><li>You can then use ft_redefinetrial to segment the data into short (non-overlapping) segments. Check it's help for details. But realize you will now define segments in terms of time, not samples.</li></ol>The benefit of this order of things is that in the first preprocessing step you can do things like filtering on the whole dataset, if you can spare the RAM.<br></div><div><br></div><div>Hope this helps,</div><div>Stephen</div><div><br></div><div><br></div><div><br></div><div><br></div></div><div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br>
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</table><a href="#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2" width="1" height="1"></a></div><div class="gmail_extra"><br><div class="gmail_quote">On 5 December 2017 at 10:55, Boukje Habets <span dir="ltr"><<a href="mailto:boukje.habets@uni-bielefeld.de" target="_blank">boukje.habets@uni-bielefeld.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear Fieldtrippers,<br><br>Im new to Fieldtrip and have a question about segmentation. I want to do a freqanalysis on EEG data (Brainvision Recorder).<br>I have one file per condition (so only containing one trigger code, and a start code at the beginning of the file) that i want to segment into 2sec pieces. Ive been trying to find a way to add a trigger with Fieldtrip, so that I can segment around a new trigger. Using a pre- and poststim timewindow around the trigger code is not a solution, as this gives me overlapping segments, which i do not want. <br>This doesnt seem possible?<br><br>After reading about cfg.trialfun, I saw that i can segment a continuous file into segments that i can define in terms of length (sec/samples). I guess this is the easiest way for me to segment my file. However, i want to be able to define the start and end point of segmentation, as my file contains a part in the beginning without codes (EEG was being recorded, but experiment was running yet). I have been playing around with the commands begsample and endsample, but that didnt change the window of segmentation (meaning it always segments my whole file, giving me 'empty' segments).<br><br>Does anybody know how to solve this?<br><br>Thanks for your time,<br><br>Boukje Habets<span class="HOEnZb"><font color="#888888"><br><br>-- <br><br>Dr. Boukje Habets<br>Biopsychology & Cognitive Neuroscience (AE14)<br>Faculty of Psychology and Sports Science | Bielefeld University<br>PO-Box 100131 | D-33501 Bielefeld, Germany<br>Phone: (49) 521 - 106 67 533 | Fax: (49) 521 - 106 15 67 530<br>Office: UHG T3-250<br>------------------------------<wbr>------------------------------<wbr>----
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