Skip to contents

Overlay plots

Source: vignettes/articles/overlay.qmd

The default cross-sectional plot places the different cross-sections in separate panels. Occasionally, it is more helpful to overlay the plots on top of one another to see more directly how they compare. Using the same model as before:

airquality$Heat <- cut(airquality$Temp, 3, labels = c("Cool", "Mild", "Hot"))
fit <- lm(Ozone ~ Solar.R + Wind * Heat, data = airquality)

We can specify overlay=TRUE to obtain a version of the plot in which all the images are overlaid:

visreg(fit, "Wind", by = "Heat", overlay = TRUE)

visreg(fit, "Heat", by = "Wind", overlay = TRUE)

The options described in cross-sectional plots work in the same way here. For example,

visreg(fit, "Heat", by = "Wind", overlay = TRUE, breaks = c(6, 12))

In particular, the option strip_names is used in the same way for consistency, even though there are no actual strips in an overlay plot:

visreg(fit, "Wind", by = "Heat", overlay = TRUE, strip_names = c("Cold", "Not so hot", "Really hot"))

Changing the appearance of lines and points that are common to all levels of by is accomplished in the same manner as other visreg plots:

visreg(fit, "Wind", by = "Heat", overlay = TRUE, line = list(linewidth = 1))

Since the colors of the lines, points, and bands in an overlay plot are mapped to the levels of by, changing them level-by-level is done the usual ggplot2 way, by adding a scale to the returned plot:

visreg(fit, "Wind", by = "Heat", overlay = TRUE) +
  scale_color_manual(values = c("#00C1C9", "#D63EFF", "#FF4E37")) +
  scale_fill_manual(values = c("#00C1C980", "#D63EFF80", "#FF4E3780"))