erpR (version 0.2.0)

erp.mean: Calculate the mean of several ERP data frames in a given time window

Description

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.

Usage

erp.mean(base, numbers, win.ini, win.end, erplist = NULL, 
startmsec=-200, endmsec=1200, others=NULL, format="long", 
name.dep="Dep", name.newvar="electrode")

Arguments

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".

Value

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).

Details

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".

See Also

erp.peak, erp.latency, rearrange, mean

Examples

data(ERPsets)

dat=erp.mean(base="Exp1_word_subj", numbers=1:20, 
win.ini=130, win.end=190, erplist=ERPsets, startmsec=-200, endmsec=1500,
others=c(condition="word", interval="130-190"), name.dep="Ampl", format="long")