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

Rodrigo Montefusco rmontefusco at med.uchile.cl
Fri Jun 13 16:36:11 CEST 2014

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."



On Fri, Jun 13, 2014 at 7:08 AM, Aaron Schurger <aaron.schurger at gmail.com>

> 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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> fieldtrip at donders.ru.nl
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