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Combine eegUtils objects

Source: R/data_combine.R
eeg_combine.Rd

Combine multiple eeg_epochs, eeg_data, or eeg_evoked objects into a single object. The function will check the participant_id entry in the epochs structure of each object to see if the objects come from a single participant or from multiple participants. If the data are from multiple participants, it will create an eeg_group object. For individual participants, it will check for duplicate epochs. For most objects, it will concatenate the objects if none are found. However, for eeg_data it will instead try to correct the epoch numbers. Check the details below for further advice.

Usage

eeg_combine(data, ...)

# S3 method for class 'list'
eeg_combine(data, ...)

# S3 method for class 'eeg_data'
eeg_combine(data, ..., check_timings = TRUE)

# S3 method for class 'eeg_epochs'
eeg_combine(data, ..., check_timings = TRUE)

# S3 method for class 'eeg_evoked'
eeg_combine(data, ...)

Arguments

data

An eeg_data, eeg_epochs, or eeg_evoked object, or a list of such objects.

...

additional eeg_data or eeg_epochs objects

check_timings

Check whether sample times / epoch numbers are continuously ascending; if not, modify so that they are. Useful when, for example, combining epochs derived from multiple recording blocks. Defaults to TRUE

Value

If all objects have the same participant_id, returns an object of the same class as the original input object. If the objects have different participant_id numbers, an object of both class eeg_group and the same class as the original input object.

Methods (by class)

  • eeg_combine(list): Method for combining lists of eeg_data and eeg_epochs objects.

  • eeg_combine(eeg_data): Method for combining eeg_data objects.

  • eeg_combine(eeg_epochs): Method for combining eeg_epochs objects

  • eeg_combine(eeg_evoked): Method for combining eeg_evoked objects

Combining eeg_data objects

Combining eeg_data is mainly intended to be used for combining multiple recordings from a single participant prior to subsequent epoching. Thus, check_timings defaults to true, and the function will change the epochs and timing structures of the resulting combined object to be as if it were a single recording. The objects will be combined in the input order, so ensure that the objects are input in chronological order.

Combining eeg_epochs objects

There are several scenarios where you might wish to combine eeg_epochs. For example, a user may have processed continuous data in smaller chunks reflecting short recording blocks before epoching. They then wish to combine these into a single object. In that case, the epoch numbering should reflect chronological ordering and needs to be corrected.

If check_timings == TRUE, the function will perform several checks before combining objects. First, it will check for duplicate epochs in the epochs structure of each object. If each object only has unique epochs, the objects will be combined without correction. Thus, combining across separate recordings or separate participants will not elicit correction. The user should ensure

If there are any duplicates (e.g. a participant has more than one epoch numbered one from the same recording), it will then check if there are any missing epochs. If there are, the new trial numbering cannot be automatically determined, so the objects cannot be combined without further manual intervention. If there are no missing epochs, it will then check if there is any decreases in epoch numbers across objects. If there are any, then the epoch numbers and timings for the objects will be adjusted.

Alternatively, the user may wish to combine eeg_epochs objects from different participants or from entirely different recording sessions of the same participant. In this case, no correction of timings or epoch numbers is desirable. check_timings == TRUE should detect this and skip correction, but can be explicitly set to FALSE.

Author

Matt Craddock, matt@mattcraddock.com