erp.mean: Calculate the mean of several ERP data frames in a given time...
In erpR: Event-Related Potentials (ERP) Analysis, Graphics and Utility Functions

Description Usage Arguments Details Value Note Author(s) See Also Examples

This function calculates the mean amplitude of several ERP data frames. It returns the results in wide format (each electrode in a separate column) or in long format which is more suitable for standard statistical analysis in R (e.g. ANOVA). erp.mean applies the function mean on several ERP data frames with timepoints in rows and electrodes in columns. ERP data frames are expected to be named as a combination of strings specified in base and numbers.

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erp.mean(base, numbers, win.ini, win.end, erplist = NULL, 
startmsec=NULL, endmsec=NULL, others=NULL, format="long", 
name.dep="Dep", name.newvar="electrode")

`base`	a string indicating the beginning of the name of `data.frame` containing ERP data.
`numbers`	the numbers of the subjects to be averaged by the function.
`win.ini`	the initial edge (in ms) of the window on which the mean amplitude has to be computed.
`win.end`	the final edge (in ms) of the window on which the mean amplitude has to be computed.
`erplist`	a list containing the ERP data frames specified in `base` and `numbers`.
`startmsec`	the start time (in ms) of the ERP data frames. It can be a negative value, indicating the baseline time frame.
`endmsec`	the end time (in ms) of the ERP data frames.
`others`	the names of other variables to be included in the returned data frame. Ignored if the format is "wide".
`format`	the output format. It may be "wide" or "long".
`name.dep`	the name of the dependent variable in the returned `data.frame`. Ignored if format is "wide".
`name.newvar`	If the format is "long", the name of the new variable codifying the electrodes. Default is "electrode".

The function takes an ERP data frame with electrodes in separate columns as input. If the format is long, this function returns a data frame in long format ready for standard statistical analysis in R. The returned data frame has one column for the dependent variable and a new factor "electrode".

A ERP data frame with mean amplitude in long or wide format. Two more columns are added: the column Subject indicates the subject number; the column Subject_name reports the string retrieved from the comment of the data frame (see Details on import.erp).

This function calls rearrange.

Giorgio Arcara

erp.peak, erp.latency, rearrange, mean

data(erplistExample)

dat=erp.mean(base="Exp1_word_subj", numbers=1:20, 
win.ini=130, win.end=190, erplist=erplistExample, 
others=c(condition="word", interval="130-190"), name.dep="Ampl", format="long")