Add Residual Lines to a Plot — gf

This function adds vertical lines representing residuals from a linear model to a ggformula plot. The residuals are drawn from the observed data points to the predicted values from the model.

Usage

gf_resid(plot, model, linewidth = 0.2, ...)

Arguments

plot: A ggformula plot object, typically created with gf_point().
model: A fitted linear model object created using lm().
linewidth: A numeric value specifying the width of the residual lines. Default is 0.2.
...: Additional aesthetics passed to geom_segment(), such as color, alpha, linetype.

Value

A ggplot object with residual lines added.

Examples

# residuals can be drawn on a full data set, but with hundreds of points
# the plot gets hard to read
flipper_model <- lm(body_mass_kg ~ flipper_length_m, data = penguins)
gf_point(body_mass_kg ~ flipper_length_m, data = penguins) %>%
  gf_model(flipper_model) %>%
  gf_resid(flipper_model)


# a small sample makes the residuals much easier to see
set.seed(1)
penguins_20 <- sample(penguins, 20)

# residuals from the empty model (in blue)
empty_model <- lm(body_mass_kg ~ NULL, data = penguins_20)
gf_point(body_mass_kg ~ flipper_length_m, data = penguins_20) %>%
  gf_model(empty_model) %>%
  gf_resid(empty_model, color = "blue")


# residuals from a two-group model on a jitter plot (in firebrick)
gentoo_model <- lm(body_mass_kg ~ gentoo, data = penguins_20)
gf_jitter(body_mass_kg ~ gentoo, data = penguins_20, width = .1) %>%
  gf_model(gentoo_model) %>%
  gf_resid(gentoo_model, color = "firebrick")


# residuals from a regression model (in firebrick)
sample_flipper_model <- lm(body_mass_kg ~ flipper_length_m, data = penguins_20)
gf_point(body_mass_kg ~ flipper_length_m, data = penguins_20) %>%
  gf_model(sample_flipper_model) %>%
  gf_resid(sample_flipper_model, color = "firebrick")