# influencePlot: Regression Influence Plot In car: Companion to Applied Regression

 influencePlot R Documentation

## Regression Influence Plot

### Description

This function creates a “bubble” plot of Studentized residuals versus hat values, with the areas of the circles representing the observations proportional to the value Cook's distance. 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, ...)

## S3 method for class 'lm'
influencePlot(model, scale=10,
xlab="Hat-Values", ylab="Studentized Residuals", id=TRUE,
fill=TRUE, fill.col=carPalette()[2], fill.alpha=0.5, ...)

## S3 method for class 'lmerMod'
influencePlot(model, ...)
``````

### Arguments

 `model` a linear, generalized-linear, or linear mixed model; the `"lmerMod"` method calls the `"lm"` method and can take the same arguments. `scale` a factor to adjust the size of the circles. `xlab, ylab` axis labels. `id` settings for labelling points; see `link{showLabels}` for details. To omit point labelling, set `id=FALSE`; the default, `id=TRUE` is equivalent to `id=list(method="noteworthy", n=2, cex=1, col=carPalette()[1], location="lr")`. The default `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=list(method="identify")` for interactive point identification. `fill` if `TRUE` (the default) fill the circles, with the opacity of the filled color proportional to Cook's D, using the `alpha` function in the scales package to compute the opacity of the fill. `fill.col` color to use for the filled points, taken by default from the second element of the `carPalette` color palette. `fill.alpha` the maximum alpha (opacity) of the points. `...` 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.

### Author(s)

John Fox jfox@mcmaster.ca, minor changes by S. Weisberg sandy@umn.edu and a contribution from Michael Friendly

### References

Fox, J. (2016) Applied Regression Analysis and Generalized Linear Models, Third Edition. Sage.

Fox, J. and Weisberg, S. (2019) An R Companion to Applied Regression, Third Edition, Sage.

`cooks.distance`, `rstudent`, `alpha`, `carPalette`, `hatvalues`, `showLabels`

### Examples

``````influencePlot(lm(prestige ~ income + education, data=Duncan))
## Not run:  # requires user interaction to identify points
influencePlot(lm(prestige ~ income + education, data=Duncan),
id=list(method="identify"))

## End(Not run)
``````

car documentation built on March 31, 2023, 6:51 p.m.