[Eeglablist] re-epoching, ICA selected periods

[Tarik S Bel-Bahar]

Hello Jose a few extra notes below, best wishes.

you might need some matlab expertise to do this right via script, as eeglab
usually or always needs epochs to be of the same length for analyses within
eeglab. It is unlikely that eeglab functions handle variable length
epochs.I recommend selecting a common time period from marker A to as close
as you can to marker C, or having two kinds of epochs, one starting from
Marker A, and another going backward from marker C, but using similar
length time period. At least like this you could examine effects mainly
after marker A, and mainly before marker C, and perhaps even constrast the
conditions. There may be recent changes in the new eeglab, please review
the updates on changes made in it.








On Sat, Mar 4, 2017 at 6:48 PM, José Luis <joseluisulloafulgeri at gmail.com>
wrote:

> Hi,
> I'm sorry my question was not enough clear,
> I don't need to add another marker based on two previous markers. I need
> to epoch my data based in two markers because my period of interest is
> between a given marker A and another marker C and this interval of time is
> variable,
> I have tried to found other related threads in the EEGlab list but the
> last one was on 2013, and apparently there was no way to do it, I wanted to
> know if someone has implemented this by now,
>
> thanks,
>
> On 5 March 2017 at 00:02, Tarik S Bel-Bahar <tarikbelbahar at gmail.com>
> wrote:
>
>> Hello Jose, yes use addnewevents ? function mentioned in eeglablist.Use a
>> matlab loop to make a new list of events based on the events you have
>> already. Then epoch on the new events you've made.
>> also several past eeglablist emails exist about making lists of new
>> events and importing them
>>
>>
>> On Sat, Mar 4, 2017 at 4:54 PM, José Luis <joseluisulloafulgeri at gmail.com
>> > wrote:
>>
>>> Hi Tarik,
>>>
>>> Thanks for the input,
>>> Looks the approach we are taking is good,
>>> However, I haven't be able to epoch using two triggers, I need to select
>>> an epoch which is 0.5 sec before a trigger A, and 0.5 sec after a trigger
>>> D, is there any way to do this?,
>>>
>>> thanks for your help,
>>> best
>>> Jose
>>>
>>> On 3 March 2017 at 21:25, Tarik S Bel-Bahar <tarikbelbahar at gmail.com>
>>> wrote:
>>>
>>>> Hello Jose,
>>>>
>>>> Yes you should be able to re-epoch, then run ICA on just the epochs
>>>> without the buffer time,
>>>> and then re-apply the ICA results to the files with the buffer time,
>>>> and go from there.
>>>> You may have to insert a new trigger, but you should be able to just
>>>> "select an epoch start/end time that does include the buffer times. First
>>>> try it with one file from the gui, and use eegh to build a script for that.
>>>>
>>>> Overall, if your buffer time is under ~2 seconds, and has no large
>>>> artifacts, it would be okay to include them in the ICA. In other words,
>>>> your ICA results should look very similar with either method (with or
>>>> without the buffer periods).
>>>>
>>>> Check Makoto's general recommendations for ICA just in case, if you
>>>> haven't had a chance to.
>>>>
>>>> On Fri, Mar 3, 2017 at 10:11 AM, José Luis <
>>>> joseluisulloafulgeri at gmail.com> wrote:
>>>>
>>>>> hi,
>>>>>
>>>>> I'm analysing EEG data and want to perform ERP and time-frequency
>>>>> analyses,
>>>>> I'm doing the pre-processing with EEGlab,
>>>>> I wanted to move fast so I epoch my data and then I proceed with the
>>>>> artefact rejection. I epoch my data taken into consideration that for
>>>>> time-frequency I need a buffer zone,
>>>>> Now, I want to perform ICA but only in a selected time period of
>>>>> interest. I have several question here:
>>>>> 1) Can I do ICA in select periods of time within my epochs?
>>>>> 2) If not, I could try to re-epoch my dataset, perform ICA in the
>>>>> re-epoched (shorter) dataset, and then re-inject the weight of the ICA back
>>>>> to the original dataset), does that sound ok? I'm only interested in my
>>>>> selected time period of interest, and the rest of the signal I would use it
>>>>> because I need a buffer zone, and because long periods to compute power at
>>>>> low frequencies,
>>>>> 3) Can I epoch relative to two triggers, i.e. for a sequence of
>>>>> triggers: A, B, C, D, E I want to do from -0.5 relative to A until E,
>>>>>
>>>>> Thanks in advance for your help,
>>>>> Jose
>>>>>
>>>>> --
>>>>> José Luis ULLOA FULGERI, PhD
>>>>> +32477429007 <+32%20477%2042%2090%2007>
>>>>> +32492646477
>>>>> https://sites.google.com/site/joseluisulloafulgeri/
>>>>>
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>>>>
>>>>
>>>
>>>
>>> --
>>> José Luis ULLOA FULGERI, PhD
>>> +32477429007 <+32%20477%2042%2090%2007>
>>> +32492646477
>>> https://sites.google.com/site/joseluisulloafulgeri/
>>>
>>
>>
>
>
> --
> José Luis ULLOA FULGERI, PhD
> +32477429007 <+32%20477%2042%2090%2007>
> +32492646477
> https://sites.google.com/site/joseluisulloafulgeri/
>
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