# leverage.plots

##### Regression Leverage Plots

These functions display a generalization, due to Sall (1990), 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.

- Keywords
- hplot, regression

##### Usage

```
leverage.plots(model, term.name, ask=missing(term.name), ...)
leverage.plot(model, ...)
## S3 method for class 'lm':
leverage.plot(model, term.name,
labels=names(residuals(model)[!is.na(residuals(model))]),
identify.points=TRUE, las=par('las'), col=palette()[2], pch=1, lwd=2,
main="Leverage Plot", ...)
## S3 method for class 'glm':
leverage.plot(model, ...)
```

##### Arguments

- model
- model object produced by
`lm`

- term.name
- name of term in the model to be plotted; this argument is usually
omitted for
`leverage.plots`

. - ask
- if
`TRUE`

, a menu is provided in the R Console for the user to select the term(s) to plot. - labels
- observation names.
- identify.points
- if
`TRUE`

, then identify points interactively. - las
- if
`0`

, ticks labels are drawn parallel to the axis; set to`1`

for horizontal labels (see`par`

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

and`par`

). - pch
- plotting character for points; default is
`1`

(a circle, see`par`

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

(see`par`

). - main
- title for plot.
- ...
- arguments passed down to method functions.

##### Details

The function intended for direct use is `leverage.plots`

. By default, this
function is used interactively through a text menu.
The model can contain factors and interactions. A leverage plot can be
drawn for each term in the model, including the constant.
`leverage.plot.glm`

is a dummy function, which generates an error message.

##### Value

`NULL`

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

##### References

Fox, J. (1997)
*Applied Regression, Linear Models, and Related Methods.* Sage.
Sall, J. (1990)
Leverage plots for general linear hypotheses.
*American Statistician* **44**, 308--315.

##### See Also

##### Examples

```
data(Duncan)
leverage.plots(lm(prestige~(income+education)*type, data=Duncan))
```

*Documentation reproduced from package car, version 1.0-14, License: GPL version 2 or newer*