Package 'visreg'

Title Visualization of regression models
Version 1.1-1
Date 2012-11-14
Author Patrick Breheny, Woodrow Burchett
Package ‘visreg’
November 14, 2012
Maintainer Patrick Breheny
Depends lattice
Suggests rgl, survival, MASS
Description Provides convenient interface for constructing plots to
visualize the fit of regression models arising from a wide
variety of models in R (lm, glm, coxph, rlm, gam, locfit, etc.)
License GPL-2
URL http://web.as.uky.edu/statistics/users/pbreheny/publications/visreg.pdf
Repository CRAN
Date/Publication 2012-11-14 21:09:16
R topics documented:
visreg-package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
visreg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
visreg2d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Index 8
1

2 visreg-package
visreg-package
Visualization of regression functions
Description
Details
visreg provides a number of plotting functions for visualizing fitted regression models: regression
functions, confidence bands, partial residuals, interactions, and more.
Package: visreg
Type: Package
Version: 1.0-0
Date: 2011-08-09
License: GPL-2
LazyLoad: yes
This package allows the use of visreg and visreg2d, both R functions used to visualize regression
functions. See the examples below for some basic uses and look in the help pages for each function
for a much more detailed look.
Author(s)
Patrick Breheny and Woodrow Burchett
Maintainer: Patrick Breheny
References
Breheny, P. and Burchett, W. (2012), Visualizing regression models using visreg. http://web.as.
uky.edu/statistics/users/pbreheny/publications/visreg.pdf
See Also
visreg visreg2d
Examples
ozone

visreg 3
visreg
Visualization of regression functions for a single variable
Description
A function used to visualize regression models quickly and easily. Default plots contain a confidence
band, prediction line, and partial residuals. Factors, transformations, conditioning, interactions,
and a variety of other options are supported.
Usage
visreg(fit, xvar, by, breaks=4, type=c("conditional","effect"), trans=I, scale=c("linear","response"
Arguments
fit
xvar
by
breaks
type
trans
scale
xtrans
alpha
nn
This is the fitted model object you wish to visualize. lm, glm, gam, rlm, and
coxph data classes are all supported.
This is the variable to be put on the x-axis of your plot. Both continuous variables
and factors are supported.
An option to use if you wish to divide your plot by a third variable. Uses the
lattice package. Both continuous variables and factors are supported.
If a continuous variable is used for the ’by’ option, the ’breaks’ argument determines
how many quantiles will be divided to be used for panels.
The type of plot to be produced. The following options are supported:
• If ’conditional’ is selected, the plot returned shows the value of the variable
on the x-axis and the change in response on the y-axis, holding all
other variables constant (median for numeric variables and most common
category for factors, by default). For more detail, see references.
• If ’effect’ is selected, the plot returned shows the effect on the expected
value of the response by moving the x variable away from a reference point
on the x-axis (median for numeric variables and most common category for
factors, by default). For more detail, see references.
Allows transformations to the response. A function should be passed (see examples).
If response is selected and a glm is passed as the fit parameter, the response will
automatically be transformed.
Allows transformations to the x-axis. A function should be passed. Note that
inverse transformations to explanatory variables are performed automatically
byvisreg.
Alpha level for the confidence band displayed in the plot.
Controls the smoothness of the line and confidence band. The higher the number,
the smoother they will appear.

4 visreg
Value
cond
whitespace
partial
jitter
strip.names
line.par
fill.par
points.par
Used to set variables to specific values. Can also be used to select the reference
point for an effect plot. Named lists should be passed. All variables left unspecified
will be filled in with the median/most common category (see examples).
When xvar is a factor, whitespace determines the ammount of space in between
factors on the x-axis.
Determines if partial residuals are shown on the plot.
Adds a small amount of noise to xvar. Potentially useful if many observations
have exactly the same value. Default is FALSE.
When by=TRUE, adds the name of the by variable to the strip at the top of each
panel. Default is FALSE.
List of parameters (see par) to pass to lines(...) when lines are drawn in the
plots.
List of parameters (see par) to pass to polygon(...) when shaded confidence
regions are drawn in the plots.
List of parameters (see par) to pass to points(...) when partial residuals are
drawn in the plots.
... Graphical parameters can be passed to the function to customize the plots. If
by=TRUE, lattice parameters can be passed, such as layout (see examples below).
In addition to providing plots, the visreg function also invisibly returns the data frames, estimates,
confidence intervals, and residuals used in the creation of its plots (see last example).
Author(s)
Patrick Breheny and Woodrow Burchett
References
Breheny, P. and Burchett, W. (2012), Visualizing regression models using visreg. http://web.as.
uky.edu/statistics/users/pbreheny/publications/visreg.pdf
See Also
visreg2d
Examples
## Linear models
## Basic
fit

visreg 5
## Factors
airquality$Heat

6 visreg2d
visreg(fit,"Wind",cond=list(Heat="Mild"))
v

visreg2d 7
Value
cond
whitespace
Used to set variables to specific values. Can also be used to select the reference
point for an effect plot. Named lists should be passed. All variables left unspecified
will be filled in with the median/most common category (see examples).
When x (or y) is a factor, whitespace determines the ammount of space in between
factors on the x (or y) axis.
... Graphical parameters can be passed to the function to customize the plots.
In addition to providing plots, the visreg function also invisibly returns the data frames and estimates
used in the creation of its plots.
Author(s)
Patrick Breheny and Woodrow Burchett
References
Breheny, P. and Burchett, W. (2012), Visualizing regression models using visreg. http://web.as.
uky.edu/statistics/users/pbreheny/publications/visreg.pdf
See Also
visreg
Examples
ozone

Index
∗Topic graphics
visreg, 3
visreg2d, 6
∗Topic models
visreg, 3
visreg2d, 6
∗Topic package
visreg-package, 2
∗Topic regression
visreg, 3
visreg2d, 6
visreg, 2, 3
visreg-package, 2
visreg2d, 2, 6
8