[Eeglablist] How much data is interpolated for ASR cleaning

[Makoto Miyakoshi]

Dear Abby,

> I understand how to extract how many channels/samples are kept in the
cleaned dataset using EEG.etc.

Exactly... well, to be really exact, you calculate
sum(EEG.etc.clean_data_points)/length(EEG.etc.clean_data_points) to compute
the ratio of the rejected data points.

> However, I'd like to keep track of how much data had to be interpolated
while batch processing. While this information is easily accessible from
the command line (ie. Keeping 82.5% (132 seconds) of the data) - I'm not
sure where this data is saved in the data structure?

   1. Apply the cleaning mask you have in EEG.etc.clean_data_points to the
   data that are BEFORE applying ASR.
   2. Now you have two data sets with the identical length, but one is
   before and the other is after cleaning. You can perform simple subtraction
   to obtain the difference waves for visual inspection, performing
   statistics, etc.
   3. One convenient measure I recommend you to try is percent variance
   accounted for (PVAF) which is computed in this way.

PVAF = 100-100*mean(var(beforeASR-afterASR))/mean(var(beforeASR))

Note that the variance should be computed ACROSS CHANNELS (i.e., variance
across scalp maps, for each frame!)
For the reference of this calculation, see
https://www.ncbi.nlm.nih.gov/pubmed/26738014

I have one paper under review, a collaboration with UCLA Sandra Loo, in
which I calculated and reported all of the cleaning parameters and
results... but it is not accepted yet.

Makoto



On Wed, Oct 3, 2018 at 4:23 AM Dickinson, Abigail <
ADickinson at mednet.ucla.edu> wrote:

> Hi all,
>
>
> I'm hoping to use ASR cleaning, but also want to quantify the amount of
> data that is interpolated for each participant.
>
>
> I understand how to extract how many channels/samples are kept in the
> cleaned dataset using EEG.etc.
>
>
> However, I'd like to keep track of how much data had to be interpolated
> while batch processing. While this information is easily accessible from
> the command line (ie. Keeping 82.5% (132 seconds) of the data) - I'm not
> sure where this data is saved in the data structure?
>
>
> Any help would be greatly appreciated!
>
>
> Thanks in advance,
>
>
> Abby
>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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