[FieldTrip] timelock grand average can't average gradiometers?

Eelke Spaak eelke.spaak at donders.ru.nl
Thu Aug 4 14:04:44 CEST 2011


Dear Vladimir,

Thanks, I did not know about that function. However, I don't think
ft_timelockgrandaverage should automatically average sensor positions;
if the user wants this it is probably best if he/she does this
explicitly. But, I will bring it up in the next FieldTrip dev team
meeting, and see what others think (particularly Robert and
Jan-Mathijs).

Best,
Eelke

2011/8/4 Vladimir Litvak <v.litvak at ion.ucl.ac.uk>:
> Dear Eelke,
>
> Actually there is a way to average sensors which is implemented in
> ft_average_sens. Perhaps it would be a good idea to use it in
> ft_timelockgrandaverage.
>
> Best,
>
> Vladimir
>
> On Thu, Aug 4, 2011 at 7:03 AM, Eelke Spaak <eelke.spaak at donders.ru.nl> wrote:
>> Hi Eli,
>>
>> The warning message you mention regards the information about the
>> gradiometer positions, i.e. the information in the data.grad field.
>> The MEG-data recorded by the gradiometer sensors will still be
>> averaged.
>>
>> I understand the confusion, though, and agree that the message could
>> be a bit clearer.
>>
>> Best,
>> Eelke
>>
>> 2011/8/3 Kanal Eliezer <ekanal at cmu.edu>:
>>> Hello all -
>>>
>>> I'm trying to average a number of datasets collected from a Neuromag scanner. This dataset contains both magnetometer and gradiometer data. I'm trying to use ft_timelockgrandaverage to average the cleaned data, and I'm getting the following error message:
>>>
>>>> Warning: discarding gradiometer information because it cannot be averaged
>>>
>>> My question is, why not? My gradiometer data isn't different than the magnetometer data. Even more confusing, when looking in the code, it looks like it's averaging it anyway, and the resulting dataset seems to contain averaged grad data. What's the purpose of this error?
>>>
>>> Thanks,
>>> Eliezer Kanal
>>>
>>>
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>>
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