[FieldTrip] How do you prevent ft_resample from filtering your trigger channels?

[Aaron Schurger]

Hi, Rodrigo,
You are right - in fact I meant downsampling instead of decimation. I
get the two words confused sometimes. Anyway, what I mean was just
taking every n-th sample. You want to avoid doing any kind of
filtering on your trigger channels!
Best wishes,
Aaron

On Fri, Jun 13, 2014 at 4:36 PM, Rodrigo Montefusco
<rmontefusco at med.uchile.cl> wrote:
> Dear Aaron,
>
> Note that the decimation process is indeed the use of a low-pass filter and
> subsequent downsampling. As you may already know, this is to avoid aliasing.
> Otherwise is just an interpolation.
>
> "Decimation reduces the original sampling rate for a sequence to a lower
> rate, the opposite of interpolation. The decimation process filters the
> input data with a lowpass filter and then resamples the resulting smoothed
> signal at a lower rate."
>
>
> Best,
>
> Rodrigo
>
>
> On Fri, Jun 13, 2014 at 7:08 AM, Aaron Schurger <aaron.schurger at gmail.com>
> wrote:
>>
>> Hi,
>> It seems that ft_resample applies to all of the channels in the data
>> structure. During resampling fieldtrip applies a filter, which adds
>> artifacts to the step function in the trigger channels. For
>> downsampling at least it would be great if you could specify a subset
>> of channels to be downsampled by simple decimation (i.e. skip the
>> lowpass filter). Is there any built-in way to do this?
>> Thanks!
>> Aaron
>>
>> --
>> Aaron Schurger, PhD
>> Senior researcher
>> Laboratory of Cognitive Neuroscience
>> Brain-Mind Institute, Department of Life Sciences
>> École Polytechnique Fédérale de Lausanne
>> Station 19, AI 2101
>> 1015 Lausanne, Switzerland
>> +41 21 693 1771
>> aaron.schurger at epfl.ch
>> http://lnco.epfl.ch/
>>
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>
>
>
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-- 
Aaron Schurger, PhD
Senior researcher
Laboratory of Cognitive Neuroscience
Brain-Mind Institute, Department of Life Sciences
École Polytechnique Fédérale de Lausanne
Station 19, AI 2101
1015 Lausanne, Switzerland
+41 21 693 1771
aaron.schurger at epfl.ch
http://lnco.epfl.ch/