eegUtils uses S3 objects to store EEG data and associated information such as channel locations. Using different object classes for data structured in different ways ensures that the various plotting functions work consistently across different types of EEG data. For example, there are different classes for epoched (
eeg_epochs) and continuous data (
eeg_data), and for time-frequency representations of data (
eeg_data objects are the base class used for continuous data. When raw data is imported, the output is this class. Currently, this class is a list constituting the following entries:
electrode- electrode names
radius- Spherical co-ordinates (Radius is typically normalized to 1)
theta- Spherical co-ordinates (theta)
phi- Spherical co-ordinates (theta)
cart_x- Cartesian 3D coordinates
cart_y- Cartesian 3D coordinates
cart_z- Cartesian 3D coordinates
x- 2D Stereographic projection of the spherical coordinates
y- 2D Stereographic projection of the spherical coordinates
ref_chans- Labels for channels used to calculate the reference data. Can also be “average”.
excluded- Labels for any channels excluded from the reference data.
eeg_epochs objects share the same overall structure with
eeg_data objects, but some of the internals currently differ, as described below.
epochgives the epoch number to which a given event belongs
timegives the time point at which the event occurs relative to the epoch onset
event_timestill gives the time point at which the event occurs relative to the recording onset
epochgives the epoch number to which a given datapoint belongs
samplestill uniquely identifies each datapoint
timenow gives the time relative to the zero-point of the epoch, i.e. the event on which the epoch is centred.
eeg_tfr objects hold time-frequency representations of
eeg_ICA objects contain the results of an ICA decomposition applied to an
signals- individual component activations