Visualization of regression functions

Default plots contain a confidence band, prediction line, and partial residuals. Factors, transformations, conditioning, interactions, and a variety of other options are supported. The plot.visreg() function accepts a visreg object as calculated by visreg() and creates the plot.

Usage

# S3 method for class 'visreg'
plot(
  x,
  overlay = FALSE,
  print_cond = FALSE,
  partial = identical(x$meta$trans, I),
  band = TRUE,
  rug = 0,
  jitter = FALSE,
  strip_names = is.numeric(x$fit[, x$meta$by]),
  top = c("line", "points"),
  line = NULL,
  fill = NULL,
  points = NULL,
  gg = TRUE,
  ...
)

# S3 method for class 'visreg_list'
plot(x, ...)

# S3 method for class 'visreg_plot_list'
print(x, ...)

Arguments

x

A visreg or visreg_list object; see visreg().

overlay

By default, when by is specified, separate panels are used to display each cross-section. If overlay=TRUE, these cross-sections are overlaid on top of each other in a single plot.

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.

partial

If partial=TRUE (the default), partial residuals are shown on the plot.

band

If band=TRUE (the default), confidence bands are shown on the plot.

rug

Controls the appearance of a rug along the horizontal axis:

rug=0/FALSE: No rug (default)
rug=1/TRUE: Basic rug is drawn along the bottom axis
rug=2: Separate rugs drawn on the top for observations with positive residuals and on the bottom for observations with negative residuals.

jitter

If jitter=TRUE, a small amount of random noise is added to the horizontal position of partial residuals (and, if drawn, the rug). Potentially useful if many observations have exactly the same value. Only applies when xvar is continuous; for factor xvar, the horizontal spacing of points is already controlled by visreg and this argument has no effect. Default is FALSE.

strip_names

When by=TRUE, strip_names=TRUE adds the name of the by variable to the strip at the top of each panel. Default is FALSE for factors and TRUE for numeric by variables. strip_names can also be a character vector, in which case it replaces the strip names altogether with values chosen by the user.

top

By default, the fitted line is plotted on top of the partial residuals; usually this is preferable, but it does run the risk of obscuring certain residuals. To change this behavior and plot the partial residuals on top, specify top='points'.

line

List of parameters to pass to ggplot2::geom_line() (continuous xvar) or ggplot2::geom_crossbar() (factor xvar) when the fitted line is plotted.

fill

List of parameters to pass to ggplot2::geom_ribbon() (continuous xvar) or ggplot2::geom_crossbar() (factor xvar) when shaded confidence regions are plotted.

points

List of parameters to pass to ggplot2::geom_point() (continuous xvar) or ggplot2::geom_jitter() (factor xvar) when partial residuals are plotted.

gg

Deprecated, no longer has any effect.

...

Not used; present only because plot() is a generic function. An error is raised if any arguments are passed here.

Value

A ggplot object, or if x is a visreg_list(), a list of ggplot objects.

Details

If x is a visreg_list(), plot.visreg_list() is dispatched instead; it simply calls plot.visreg() on each element in turn, passing along the same arguments to each element.

References

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

Examples

fit <- lm(Ozone ~ Solar.R + Wind + Temp, data = airquality)
visreg(fit, "Wind")


# Changing appearance
visreg(fit, "Wind", line = list(color = "red"), points = list(size = 2))