This vignettes demonstrates the
plot()-method of the ggeffects-package. It is recommended to read the general introduction first, if you haven’t done this yet.
If you don’t want to write your own ggplot-code, ggeffects has a
plot()-method with some convenient defaults, which allows quickly creating ggplot-objects.
plot() has some arguments to tweak the plot-appearance. For instance,
ci allows you to show or hide confidence bands (or error bars, for discrete variables),
facets allows you to create facets even for just one grouping variable, or
colors allows you to quickly choose from some color-palettes, including black & white colored plots. Use
add.data to add the raw data points to the plot.
ggeffects supports labelled data and the
plot()-method automatically sets titles, axis - and legend-labels depending on the value and variable labels of the data.
For three grouping variable (i.e. if
terms is of length four), one plot per
panel (the values of the fourth variable in
terms) is created, and a single, integrated plot is produced by default. Use
one.plot = FALSE to return one plot per panel.
In some plots, the the confidence bands are not represented by a shaded area (ribbons), but rather by error bars (with line), dashed or dotted lines. Use
ci.style = "errorbar",
ci.style = "dash" or
ci.style = "dot" to change the style of confidence bands.
For binomial models, the y-axis indicates the predicted probabilities of an event. In this case, error bars are not symmetrical.
Here you can use
log.y to log-transform the y-axis. The
plot()-method will automatically choose axis breaks and limits that fit well to the value range and log-scale.
Furthermore, arguments in
... are passed down to
log.y = TRUE), so you can control the appearance of the y-axis.
ggpredict() also supports
coxph-models from the survival-package and is able to either plot risk-scores (the default), probabilities of survival (
type = "surv") or cumulative hazards (
type = "cumhaz").
Since probabilities of survival and cumulative hazards are changing across time, the time-variable is automatically used as x-axis in such cases, so the
terms-argument only needs up to two variables.
The ggeffects-package has a few pre-defined color-palettes that can be used with the
show_pals() to see all available palettes.
Here are two examples showing how to use pre-defined colors: