Referencing

Used to reference the EEG data to a specified electrode or electrodes. Defaults to average reference. When specific electrodes are used, they are removed from the data. Meta-data about the referencing scheme is held in the eeg_data structure.

Usage

eeg_reference(data, ...)

# Default S3 method
eeg_reference(data, ...)

# S3 method for class 'eeg_data'
eeg_reference(
  data,
  ref_chans = "average",
  exclude = NULL,
  robust = FALSE,
  implicit_ref = NULL,
  verbose = TRUE,
  ...
)

# S3 method for class 'eeg_epochs'
eeg_reference(
  data,
  ref_chans = "average",
  exclude = NULL,
  robust = FALSE,
  implicit_ref = NULL,
  verbose = TRUE,
  ...
)

Arguments

data

Data to re-reference. Primarily meant for use with data of class eeg_data.

...

Further parameters to be passed to eeg_reference

ref_chans

Channels to reference data to. Defaults to "average" i.e. average of all electrodes in data. Character vector of channel names or numbers.

exclude

Electrodes to exclude from average reference calculation.

robust

Use median instead of mean; only used for average reference. Defaults to FALSE.

implicit_ref

Implicit reference channel - use this to add a channel back that was previously used as a reference. E.g. if the LM (left mastoid) channel was used in recording and is absent from the data, passing "LM" adds an "LM" channel back to the data, populated with zeroes.

verbose

Print informative messages in console. Defaults to TRUE.

Value

object of class eeg_data, re-referenced as requested.

Methods (by class)

• eeg_reference(default): Default method

• eeg_reference(eeg_data): Rereference objects of class eeg_data

• eeg_reference(eeg_epochs): Rereference objects of class eeg_epochs

Author

Matt Craddock matt@mattcraddock.com

Examples

# demo_epochs is average referenced by default
demo_epochs
#> Epoched EEG data
#> 
#> Number of channels	: 11 
#> Number of epochs	: 80 
#> Epoch limits		: -0.197 - 0.451 seconds
#> Electrode names		: A5 A13 A21 A29 A31 B5 B6 B8 B16 B18 B26 
#> Sampling rate		: 128  Hz
#> Reference		: average 
# Rereference it but exclude B5 from calculation of the average
eeg_reference(demo_epochs, exclude = "B5")
#> You have used the existing reference channel(s), average again.
#> Epoched EEG data
#> 
#> Number of channels	: 11 
#> Number of epochs	: 80 
#> Epoch limits		: -0.197 - 0.451 seconds
#> Electrode names		: A5 A13 A21 A29 A31 B5 B6 B8 B16 B18 B26 
#> Sampling rate		: 128  Hz
#> Reference		: average 
# Reference data using the median of the reference channels rather than the mean
eeg_reference(demo_epochs, robust = TRUE)
#> You have used the existing reference channel(s), average again.
#> Epoched EEG data
#> 
#> Number of channels	: 11 
#> Number of epochs	: 80 
#> Epoch limits		: -0.197 - 0.451 seconds
#> Electrode names		: A5 A13 A21 A29 A31 B5 B6 B8 B16 B18 B26 
#> Sampling rate		: 128  Hz
#> Reference		: average 

eeg_reference(demo_spatial)
#> You have used the existing reference channel(s), average again.
#> Epoched EEG data
#> 
#> Number of channels	: 23 
#> Number of epochs	: 80 
#> Epoch limits		: -0.301 - 0.488 seconds
#> Electrode names		: Fp1 Fp2 Fz Cz Pz P3 P4 C3 C4 P7 P8 F3 F4 T7 T8 F7 F8 Oz Fpz EXG1 EXG2 EXG3 EXG4 
#> Sampling rate		: 128  Hz
#> Reference		: average 
eeg_reference(demo_spatial, ref_chans = "Fz")
#> Epoched EEG data
#> 
#> Number of channels	: 22 
#> Number of epochs	: 80 
#> Epoch limits		: -0.301 - 0.488 seconds
#> Electrode names		: Fp1 Fp2 Cz Pz P3 P4 C3 C4 P7 P8 F3 F4 T7 T8 F7 F8 Oz Fpz EXG1 EXG2 EXG3 EXG4 
#> Sampling rate		: 128  Hz
#> Reference		: Fz 
eeg_reference(demo_spatial, implicit_ref = "LM")
#> You have used the existing reference channel(s), average again.
#> Epoched EEG data
#> 
#> Number of channels	: 24 
#> Number of epochs	: 80 
#> Epoch limits		: -0.301 - 0.488 seconds
#> Electrode names		: Fp1 Fp2 Fz Cz Pz P3 P4 C3 C4 P7 P8 F3 F4 T7 T8 F7 F8 Oz Fpz EXG1 EXG2 EXG3 EXG4 LM 
#> Sampling rate		: 128  Hz
#> Reference		: average