<html dir="ltr">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css" id="owaParaStyle"></style><style type="text/css"></style>
</head>
<body fpstyle="1" ocsi="0">
<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;"><font face="Times New Roman" size="3">Hi Moran,</font>
<div><font face="Times New Roman" size="3"><br>
</font></div>
<div><font face="Times New Roman" size="3">It was a bit difficult to understand your question, but I've tried to answer them below.</font></div>
<div><font face="Times New Roman" size="3">For your main question: Yes, it is possible to cut up your EEG data into individual trials, with the time (i.e. 1 second) that you specify.</font></div>
<div><font face="Times New Roman" size="3"><br>
</font></div>
<div><font face="Times New Roman" size="3">The function that cuts up your EEG data is known as ft_definetrial. However, ft_definetrial needs to read information from another function that explicitly tells it how to do the cutting. Usually, that function is
"ft_trialfun_general" (this is the tutorial link you mentioned). However, if you have a complicated set of triggers or ways you want to cut up your data, you will be better off writing your own trialfun (" trial function").</font></div>
<div><font face="Times New Roman" size="3"><br>
</font></div>
<div><font face="Times New Roman" size="3">If you need to write your trialfun, you should
<b>check out these example scripts / tutorials</b>:<br>
http://www.fieldtriptoolbox.org/example/making_your_own_trialfun_for_conditional_trial_definition<a href="http://www.fieldtriptoolbox.org/example/making_your_own_trialfun_for_conditional_trial_definition" target="_blank">http://www.fieldtriptoolbox.org/example/making_your_own_trialfun_for_conditional_trial_definition</a></font></div>
<div><font face="Times New Roman" size="3"><br>
</font></div>
<div><font face="Times New Roman" size="3">http://www.fieldtriptoolbox.org/tutorial/eeg_preprocessing_erp<a href="http://www.fieldtriptoolbox.org/tutorial/eeg_preprocessing_erp" target="_blank">http://www.fieldtriptoolbox.org/tutorial/eeg_preprocessing_erp</a> </font></div>
<div><font face="Times New Roman" size="3"><br>
</font></div>
<div><font face="Times New Roman" size="3">To answer your " little " questions</font></div>
<div>
<div><font face="Times New Roman" size="3"><b>1.</b> cfg.trialdef.eventvalue = [3 5 9]; </font></div>
<div><font face="Times New Roman" size="3">3 5 9 are trigger codes. This tells your function to go into your data, look for these trigger codes, and cut your data with respect to the location of these triggers</font></div>
<div><font face="Times New Roman" size="3"><br>
</font></div>
<div><font face="Times New Roman" size="3">E.g., your data trigger codes look like this ----1 ----- 3 ------ 4 ------5 ----- 9 ----. <br>
In this case, the ft_definetrial will only use triggers 3, 5, and 9 as relative points for cutting your data, trigger 1 and 4 will be ignored.</font></div>
<div><font face="Times New Roman" size="3">N.B. The data at trigger 1 might end up in your time window that contains trigger 3 if you define your time window to be very. To understand this, see below.</font></div>
<div><font face="Times New Roman" size="3"><br>
</font></div>
<div><font face="Times New Roman" size="3"><b>2.</b> cfg.trialdef.prestim = 1; </font></div>
<div><font face="Times New Roman" size="3">cfg.trialdef.poststim = 2;</font></div>
</div>
<div><font face="Times New Roman" size="3"><br>
</font></div>
<div><font face="Times New Roman" size="3">These 2 parameters are important. The values are defined in seconds. So cfg.trialdef.prestim refers to 1s before your trigger (i.e. prestim = prestimulus onset, where stimulus onset is referred to the sample point
of your chosen trigger). cfg.trialdef.poststim refers to 2s after your trigger.</font></div>
<div><font face="Times New Roman" size="3">In this way you would end up with a 3 second time window (1 second before trigger, and 2 seconds after). </font></div>
<div><font face="Times New Roman" size="3"><br>
</font></div>
<div><font face="Times New Roman" size="3">You mentioned you wanted " specific time [in data] + one second".</font></div>
<div><font face="Times New Roman" size="3">So you 1) determine which triggers mark the " specific time [in your data]"</font></div>
<div><font face="Times New Roman" size="3">2) specify cfg.trialdef.poststim = 1. </font></div>
<div><font face="Times New Roman" size="3"><br>
</font></div>
<div><font face="Times New Roman" size="3">Hope this helps and good luck,</font></div>
<div><font face="Times New Roman" size="3">Nietzsche </font></div>
<div>
<div style="font-family: Times New Roman; color: #000000; font-size: 16px">
<hr tabindex="-1">
<div id="divRpF136729" style="direction: ltr;"><font face="Tahoma" size="2" color="#000000"><b>From:</b> fieldtrip-bounces@science.ru.nl [fieldtrip-bounces@science.ru.nl] on behalf of moran abilea [mor2451@gmail.com]<br>
<b>Sent:</b> 28 May 2015 16:56<br>
<b>To:</b> FieldTrip discussion list<br>
<b>Subject:</b> [FieldTrip] using triggers building my own function<br>
</font><br>
</div>
<div></div>
<div>
<div dir="ltr">hi everyone,
<div>so i'm trying to create my own function for using triggers with EEG raw data.</div>
<div>i used this tutorial:</div>
<div><a href="http://www.fieldtriptoolbox.org/tutorial/preprocessing" target="_blank">http://www.fieldtriptoolbox.org/tutorial/preprocessing</a><br>
</div>
<div><br>
</div>
<div>my question is if i can somehow specify the time i want to record my EEG data?</div>
<div>for example i would like my function to get 'time' as parameter to the function and returns the EEG raw data of this specific time+one second.</div>
<div>if so, can some one give me a piece of code for example to understand what to do?</div>
<div><br>
</div>
<div>also 2 more little questions:</div>
<div>1. cfg.trialdef.eventvalue = [3 5 9]; what does the 3 5 9 stands for? i don't understand what is the meaning of those (or any other) numbers. can i get definition for what is event value?</div>
<div>2. cfg.trialdef.prestim = 1; </div>
<div>cfg.trialdef.poststim = 2;</div>
<div>does it means it takes exactly one second for the buffer to give me the EEG raw data? or does it means wait one second and then take the data from the buffer or something like that (1 second the trigger will "pop out" and finish taking the data from the
buffer after 2 seconds)</div>
<div><br>
</div>
<div>the triggers are new to me, so i have some problems to understand the concept of it, thus my questions for you guys.</div>
<div><br>
</div>
<div>i hope i explained myself as clear as possible, i really would like to understand what i'm doing.</div>
<div><br>
</div>
<div>regards,</div>
<div>Moran Abilea</div>
</div>
</div>
</div>
</div>
</div>
</body>
</html>