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craddm / eegUtils

An R package for processing and plotting of electroencephalography (EEG) data
https://craddm.github.io/eegUtils/
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Issue: function epoch_data() #108

Closed DrCri95 closed 3 years ago

DrCri95 commented 3 years ago

Hi,

First of all, thanks a lot for this R package, really useful!

I've been preprocessing EEG data (n = 40 participants) and everything is okay for 38 datasets. However, I got this error in 2 datasets when extracting epochs. I've been reviewing these 2 files in more detail and I could not find any issue within these datasets (correct events, correct signals, and so on).

epoch_data(eeg_data, events = c(55, 56), epoch_labels = c("right","left"), time_lim = c(-0.2, 3.0), baseline = c(-.2, 0))

Error in dim(base_times$signals) <- c(n_bl_times, n_epochs, n_chans) : 
  dims [product 3336216] do not match the length of object [3329280]

Thanks!

craddm commented 3 years ago

Hi,

Right, I know exactly where the error occurs but not exactly why. Somehow there's a mismatch between the number of times extracted for the baseline and the product of the number of trials, number of epochs, and number of channels, which suggests to me there might be either an extra epoch or an extra channel somewhere. An extra epoch seems more likely to me. I need a bit more info about the data (or ideally one of the problematic data files) - sampling rate? number of channels?

Another couple of questions - if you try a different baseline period, does it work? If you don't subtract the baseline at all, does it work? Does subsequently subtracting the baseline work? If you epoch it without subtracting the baseline, check the epoch structure using epochs(your_epoched_data) - are there the right number of epochs? I suspect there might be multiple rows for one epoch in the epochs structure... so instead of, say epoch 10 having one row, there are two rows with epoch number 10... if so, I've an easy fix in mind :)

Cheers, Matt

craddm commented 3 years ago

This might be fixed on the dev branch now.

Matt

DrCri95 commented 3 years ago

Hi Matt,

Thank you very much for your quick response!

Until today I have not been able to do the checks you have suggested. The good news is that my problem has been solved, I have extracted the epochs without getting any errors, after having installed the latest development version.

Cheers, Cris