erp.peak: calculate the peak 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) References See Also Examples

This function calculates the peak amplitude on several ERP data frame. It returns 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.peak applies the function mean to 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.peak(base, numbers, win.ini, win.end, erplist = NULL,
startmsec=NULL, endmsec=NULL, others=NULL, format="long", 
name.dep="Dep", name.newvar="electrode", peak.fun = "max", ...)

`base`	a string indicating the beginning of the name of `data.frame` containing the 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 peak amplitude has to be computed.
`win.end`	the final edge (in ms) of the window on which the peak 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 the format is "wide".
`peak.fun`	the function to calculate the peak. Available functions are `max`, `min`, `localmax`, `localmin`.
`name.newvar`	If the format is "long", the name of the new variable codifying the electrodes. Default is "electrode".
`...`	arguments passed to the function specified in `peak.fun`.

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 dependent variable and a new factor "electrode". The erpR functions localmax and localmin are are written following Luck (2005).

A ERP data frame with peak 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

Luck, S., J. (2005). An Introduction to the Event-Related Potential Technique. Cambridge, Mass.: The MIT Press.

erp.mean, erp.latency, rearrange, max, min, localmax, localmin

data(erplistExample)

dat=erp.peak(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", peak.fun=max)