R: Regression Leverage Plots

leveragePlots {car}

R Documentation

Regression Leverage Plots

Description

These functions display a generalization, due to Sall (1990) and Cook and Weisberg (1991), of added-variable plots to multiple-df terms in a linear model. When a term has just 1 df, the leverage plot is a rescaled version of the usual added-variable (partial-regression) plot.

Usage

leveragePlots(model, terms = ~., layout = NULL, ask, 
    main, ...)

leveragePlot(model, ...)

## S3 method for class 'lm'
leveragePlot(model, term.name,
    id.method = list(abs(residuals(model, type="pearson")), "x"),
    labels, 
    id.n = if(id.method[1]=="identify") Inf else 0,
    id.cex=1, id.col=palette()[1], 
    col=palette()[1], col.lines=palette()[2], lwd=2, 
    xlab, ylab, main="Leverage Plot", grid=TRUE, ...)

## S3 method for class 'glm'
leveragePlot(model, ...)

Arguments

`model`	model object produced by `lm`
`terms`	A one-sided formula that specifies a subset of the predictors. One added-variable plot is drawn for each term. The default `~.` is to plot against all numeric predictors. For example, the specification `terms = ~ . - X3` would plot against all predictors except for `X3`. If this argument is a quoted name of one of the predictors, the added-variable plot is drawn for that predictor only.
`layout`	If set to a value like `c(1, 1)` or `c(4, 3)`, the layout of the graph will have this many rows and columns. If not set, the program will select an appropriate layout. If the number of graphs exceed nine, you must select the layout yourself, or you will get a maximum of nine per page. If `layout=NA`, the function does not set the layout and the user can use the `par` function to control the layout, for example to have plots from two models in the same graphics window.
`ask`	if `TRUE`, a menu is provided in the R Console for the user to select the term(s) to plot.
`xlab, ylab`	axis labels; if missing, labels will be supplied.
`main`	title for plot; if missing, a title will be supplied.
`...`	arguments passed down to method functions.
`term.name`	Quoted name of term in the model to be plotted; this argument is omitted for `leveragePlots`.
`id.method,labels,id.n,id.cex,id.col`	Arguments for the labelling of points. The default is `id.n=0` for labeling no points. See `showLabels` for details of these arguments.
`col`	color(s) of points
`col.lines`	color of the fitted line
`lwd`	line width; default is `2` (see `par`).
`grid`	If TRUE, the default, a light-gray background grid is put on the graph

Details

The function intended for direct use is leveragePlots.

The model can contain factors and interactions. A leverage plot can be drawn for each term in the model, including the constant.

leveragePlot.glm is a dummy function, which generates an error message.

Value

NULL. These functions are used for their side effect: producing plots.

Author(s)

John Fox jfox@mcmaster.ca

References

Cook, R. D. and Weisberg, S. (1991). Added Variable Plots in Linear Regression. In Stahel, W. and Weisberg, S. (eds.), Directions in Robust Statistics and Diagnostics. Springer, 47-60.

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.

Sall, J. (1990) Leverage plots for general linear hypotheses. American Statistician 44, 308–315.

Examples

leveragePlots(lm(prestige~(income+education)*type, data=Duncan))

[Package car version 2.0-12 Index]