inspect the influence of a subject on an average (scalp array)

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Description

The function returns a diagnostic plot to investigate the influence of a given ERP data frame on the grandaverage of a series of ERP data frames. A GUI is provided to explore the effect of removing a data frame (that is expected to be associated with a subject) from the grandaverage. Two plots are superposed: the original grandaverage, and the average removing the subject selected via the GUI. The plot shows an array of electrodes with a topography reflecting their positions on the scalp.

Usage

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scalp.infl(base, numbers, smo = NULL, layout = 1, outnumber=1,
ylims = 12,  yrev = FALSE, startmsec = -200, endmsec = 1200, 
lwd = c(1, 2), lty = 1, col = "black", out.col = "red", 
erplist = NULL, t.axis=seq(-100,endmsec,200), scalp.array=NULL)

Arguments

base

a string indicating the beginning of the name of the data.frame containing the ERP data.

numbers

the numbers of the subjects to be averaged.

smo

the smoothing parameter to apply (see smooth.spline). Default is NULL and no smoothing is applied.

layout

A number indicating the layout of electrodes to be plotted. Currently only few default layouts are supported (a number from 1 to 5). Alternatively, a character vector specifying the layout may be supplied (see Details).

outnumber

The number of the subject that will be initially removed from the averaged (this value could be changed also via the GUI).

ylims

a number indicating the upper and lower limits of the y axis. If "auto", the function calculates the y limits automatically.

yrev

logical. If TRUE, the y-axis is plotted with the negative values upward.

startmsec

the start time (in ms) of the ERP vector

endmsec

the end time (in ms) of the ERP vector

lwd

line width of the waveforms.

lty

line type of the waveforms.

col

the color of the grand average including all subjects.

out.col

the color of the grand average in which the selected subject is removed

erplist

a list containing ERP data frames.

t.axis

the position of the ticks on an additional axis indicating the time. This axis is plotted in the bottom-left corner of the plot array.

scalp.array

This argument is vector of two values indicating the number of panels of the plot, as number of rows and number of columns respectively. If a default layout is specified, the number of panels is automatically computed. See also Details.

Details

The layout parameter can be a number (from 1 to 5), that specifies some default electrode arrangements (currently only a few default arrangements are supported). Otherwise, the argument may be a character vector indicating the names of the electrodes to be plotted. The plot is divided in a number of panels as specified in scalp.array. The names specified will be plotted from top to bottom and from left to right. If "blank" is specified an empty panel will be plotted. If "xaxis" is specified a x axis indicating time will be plotted. If "yaxis" is specified a y axis indicating voltage will be plotted.

Value

The function returns a plot of a scalp array showing the influence of a subject on the grandaverage.

Author(s)

Giorgio Arcara

See Also

erp.infl, scalp

Examples

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data(ERPsets)

# Notice that Subject 1 is clearly particularly influential 
# for the average on OZ.
scalp.infl(base="Exp1_word_subj", numbers=1:20, layout=1, 
startmsec=-200, endmsec=1500, erplist=ERPsets)

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