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 = ifelse(partial, 0, 2),
  strip_names = is.numeric(x$fit[, x$meta$by]),
  top = c("line", "points"),
  line = NULL,
  fill = NULL,
  points = NULL,
  ...
)

# S3 method for class 'visreg_list'
plot(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: By default, partial residuals are plotted. Alternatively, a rug may be plotted along the horizontal axis instead. Setting rug=TRUE turns off partial residuals by default; if one wants both to be plotted, both rug=TRUE and partial=TRUE need to be specified. Two types of rug plots are available. If rug=1 or rug=TRUE, then a basic rug is drawn on the bottom. If rug=2, then separate rugs are drawn on the top for observations with positive residuals and on the bottom for observations with negative residuals. Such plots are particularly useful in logistic regression (see examples).
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.
...: Not used.

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", line = list(color = "red"), points = list(size = 1, shape = 1))


# Changing appearance
visreg(fit, "Wind", line = list(color = "red"), points = list(size = 1, shape = 1))