car (version 2.1-2)

influencePlot: Regression Influence Plot

Description

This function creates a “bubble” plot of Studentized residuals by hat values, with the areas of the circles representing the observations proportional to Cook's distances. Vertical reference lines are drawn at twice and three times the average hat value, horizontal reference lines at -2, 0, and 2 on the Studentized-residual scale.

Usage

influencePlot(model, ...)
"influencePlot"(model, scale=10, 
	xlab="Hat-Values", ylab="Studentized Residuals",  labels, id.method = "noteworthy", id.n = if(id.method[1]=="identify") Inf else 0,  id.cex=1, id.col=palette()[1], ...)

Arguments

model

a linear or generalized-linear model.

scale

a factor to adjust the size of the circles.

xlab, ylab

axis labels.

labels, id.method, id.n, id.cex, id.col

settings for labelling points; see link{showLabels} for details. To omit point labelling, set id.n=0, the default. The default id.method="noteworthy" is used only in this function and indicates setting labels for points with large Studentized residuals, hat-values or Cook's distances. Set id.method="identify" for interactive point identification.

...

arguments to pass to the plot and points functions.

Value

If points are identified, returns a data frame with the hat values, Studentized residuals and Cook's distance of the identified points. If no points are identified, nothing is returned. This function is primarily used for its side-effect of drawing a plot.

References

Fox, J. (2008) Applied Regression Analysis and Generalized Linear Models, Second Edition. Sage. Fox, J. and Weisberg, S. (2011) An R Companion to Applied Regression, Second Edition, Sage.

See Also

cooks.distance, rstudent, hatvalues, showLabels

Examples

influencePlot(lm(prestige ~ income + education, data=Duncan))