# avPlots

From car v2.0-11
by John Fox

##### Added-Variable Plots

These functions construct added-variable (also called partial-regression) plots for linear and generalized linear models.

- Keywords
- hplot, regression

##### Usage

```
avPlots(model, terms=~., intercept=FALSE, layout=NULL, ask, main, ...)
avp(...)
avPlot(model, ...)
## S3 method for class 'lm':
avPlot(model, variable,
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],
xlab, ylab, pch = 1, lwd = 2,
main=paste("Added-Variable Plot:", variable),
grid=TRUE,
ellipse=FALSE, ellipse.args=NULL, ...)
## S3 method for class 'glm':
avPlot(model, variable,
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],
xlab, ylab, pch = 1, lwd = 2, type=c("Wang", "Weisberg"),
main=paste("Added-Variable Plot:", variable), grid=TRUE,
ellipse=FALSE, ellipse.args=NULL, ...)
```

##### Arguments

- model
- model object produced by
`lm`

or`glm`

. - terms
- A one-sided formula that specifies a subset of the predictors.
One added-variable plot is drawn for each term. For example, the
specification
`terms = ~.-X3`

would plot against all terms except for`X3`

. If this argument is a q - intercept
- Include the intercept in the plots; default is
`FALSE`

. - variable
- A quoted string giving the name of a regressor in the model matrix for the horizontal axis
- 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 la - main
- The title of the plot; if missing, one will be supplied.
- ask
- If
`TRUE`

, ask the user before drawing the next plot; if`FALSE`

don't ask. - ...
`avPlots`

passes these arguments to`avPlot`

.`avPlot`

passes them to`plot`

.- 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 for points; the default is the
*second*entry in the current color palette (see`palette`

and`par`

). - col.lines
- color for the fitted line.
- pch
- plotting character for points; default is
`1`

(a circle, see`par`

). - lwd
- line width; default is
`2`

(see`par`

). - xlab
- x-axis label. If omitted a label will be constructed.
- ylab
- y-axis label. If omitted a label will be constructed.
- type
- if
`"Wang"`

use the method of Wang (1985); if`"Weisberg"`

use the method in the Arc software associated with Cook and Weisberg (1999). - grid
- If
`TRUE`

, the default, a light-gray background grid is put on the graph. - ellipse
- If
`TRUE`

, plot a concentration ellipse; default is`FALSE`

. - ellipse.args
- Arguments to pass to the
`link{dataEllipse}`

function, in the form of a list with named elements; e.g.,`ellipse.args=list(robust=TRUE))`

will cause the ellipse to be plotted using a robust covariance-matrix.

##### Details

The function intended for direct use is `avPlots`

(for which `avp`

is an abbreviation).

##### Value

- These functions are used for their side effect id producing plots, but also invisibly return the coordinates of the plotted points.

##### References

Cook, R. D. and Weisberg, S. (1999)
*Applied Regression, Including Computing and Graphics.* Wiley.
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.
Wang, P C. (1985)
Adding a variable in generalized linear models.
*Technometrics* **27**, 273--276.
Weisberg, S. (2005) *Applied Linear Regression*, Third Edition, Wiley.

##### See Also

`residualPlots`

, `crPlots`

, `ceresPlots`

, `link{dataEllipse}`

##### Examples

```
avPlots(lm(prestige~income+education+type, data=Duncan))
avPlots(glm(partic != "not.work" ~ hincome + children,
data=Womenlf, family=binomial))
```

*Documentation reproduced from package car, version 2.0-11, License: GPL (>= 2)*

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