[FieldTrip] missing channels and time locked grand average

[Arnold Kochari]

Hi Arjen,

Thank you for the suggestion. I tried it, but in this case
ft_timelockgrandaverage
just spits out NaN for the channels where some participant(s) had NaNs.
This is to be expected since that's how Matlab deals with NaNs by default. So
basically I need to find some way to do averaging within the filedtrip
datastructure that would be equivalent to matlab's 'omitnan' option.



Arnold


On Fri, Aug 4, 2017 at 5:20 PM, Arjen Stolk <a.stolk8 at gmail.com> wrote:

> Hi Arnold,
>
> There's a cfg.method = 'nan' option in ft_channelrepair, which creates NaN
> data for specified channels. As a result, these channels are still
> considered in the group-level statistics, provided other subjects have data
> for the same channels. However, I don't know whether timelockgrandaverage
> can yet deal with these NaN channels too.
>
> Best,
> Arjen
>
> On Fri, Aug 4, 2017 at 7:45 AM, Arnold Kochari <a.kochari at uva.nl> wrote:
>
>> Dear FieldTrip community,
>>
>> I have a question about what seems to be an old problem with no solution
>> posted yet.
>>
>> I have deleted bad channels in some participants during preprocessing.
>> Now I would like to compute grand average ERPs
>> using ft_timelockgrandaverage. However, if a channel has been deleted in at
>> least one participant, the mean for it does not get calculated. What I
>> would like to see is just that the average is calculated among the
>> remaining participants.
>>
>> I understand that there might be some strong arguments for the absence of
>> this functionality. I also know about the possibility to interpolate the
>> deleted channels using channelrepair, but I do not really agree with it.
>>
>> Is there any way to calculate grand averages the way I would like to do
>> it? The only solution that I can think of right now is exporting the data,
>> making the calculation in R and then importing the averages it again, but
>> that would require a lot f time.
>>
>>
>> Kind regards,
>> Arnold Kochari
>> PhD candidate, Institute for Logic, Language and Computation, University
>> of Amsterdam
>>
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>
>
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