Visualization of regression functions for two variables

Plot method for visualizing how two variables interact to affect the response in regression models.

Usage

# S3 method for class 'visreg2d'
plot(
  x,
  plot.type = c("image", "persp", "rgl", "gg"),
  xlab,
  ylab,
  zlab,
  color,
  print_cond = FALSE,
  whitespace = 0.2,
  ...
)

Arguments

x

A visreg2d() object.

plot.type

The style of plot to be produced. The following options are supported:

• image: a filled contour

• gg: a filled contour plot using ggplot2

• persp: a 3 dimensional perspective plot

• rgl: a version of the perspective plot that can be rotated (requires the rgl package to be installed)

xlab

Axis label for x variable

ylab

Axis label for y variable

zlab

Axis label for outcome

color

For plot.type='persp' or plot.type='rgl', the color of the surface. For plot.type='image' or plot.type='gg', a vector of colors used to establish a color palette.

print_cond

If print_cond==TRUE, the explanatory variable values conditioned on in a conditional plot are printed to the console (default: FALSE). If print_cond==TRUE and type=="contrast", the conditions will still be printed, but they have no bearing on the plot unless interactions are present.

whitespace

When xvar or yvar is a factor, whitespace determines the amount of space in between the factors. Default is 0.2, meaning that 20 percent of the axis is whitespace.

...

Graphical parameters can be passed to the function to customize the plots.

References

Breheny P and Burchett W. (2017) Visualization of regression models using visreg. R Journal, 9: 56-71. doi:10.32614/RJ-2017-046

See also

visreg2d() for creating two-dimensional visreg objects, and the surface plots vignette for examples and details.

Examples

fit <- lm(
  Ozone ~ Solar.R + Wind + Temp + I(Wind^2) + I(Temp^2) +
    I(Wind * Temp) + I(Wind * Temp^2) + I(Temp * Wind^2) + I(Temp^2 * Wind^2),
  data = airquality
)

visreg2d(fit, x = "Wind", y = "Temp", plot.type = "image")

visreg2d(fit,
  x = "Wind", y = "Temp", plot.type = "image",
  color = c("purple", "green", "red")
)

visreg2d(fit, x = "Wind", y = "Temp", plot.type = "persp")


## Requires the rgl package
# \donttest{
visreg2d(fit, x = "Wind", y = "Temp", plot.type = "rgl")
#> Loading required namespace: rgl
#> Warning: RGL: unable to open X11 display
#> Warning: 'rgl.init' failed, will use the null device.
#> See '?rgl.useNULL' for ways to avoid this warning.
# }

## Requires the ggplot2 package
# \donttest{
visreg2d(fit, x = "Wind", y = "Temp", plot.type = "gg")

# }