Bland-Altman plot

R code of the ggplot2 example

library(ggplot2)
library(dplyr)
library(carData)

## Record 12 has weight and height swapped (166 kg, 57 cm): left out.
weights <- Davis[-12, ] |>
  filter(!is.na(repwt)) |>
  mutate(mean = (weight + repwt) / 2, gap = repwt - weight)
bias <- mean(weights$gap)
limits <- bias + c(-1, 1) * qnorm(0.975) * sd(weights$gap)

p <- ggplot(weights, aes(x = mean, y = gap)) +
  geom_hline(yintercept = bias, colour = "#535353", linewidth = 0.4) +
  geom_hline(yintercept = limits, colour = "#9b2367", linewidth = 0.4, linetype = "dashed") +
  geom_point(size = 1.2, alpha = 0.5, colour = "#535353", position = position_jitter(0.2, 0.15, seed = 1)) +
  annotate("text", x = 118, y = limits + c(-0.6, 0.6), label = c("Lower limit", "Upper limit"),
           hjust = 1, size = 3, colour = "#9b2367") +
  annotate("text", x = 118, y = bias + 0.6, label = "Mean gap", hjust = 1, size = 3, colour = "#535353") +
  scale_x_continuous(labels = lex_number, breaks = lex_break_breaks, expand = lex_break_expand) +
  scale_y_continuous(labels = lex_number) +
  labs(title = "Reported and measured weights agree within ±4.5 kg",
       subtitle = "182 adults; limits of agreement at 95%, points slightly jittered",
       x = "Mean of reported and measured weight (kg)", y = "Reported − measured (kg)",
       caption = "Data: Davis 1990, via the carData R package") +
  theme_lex_viz(grid = "y", arrows = "x", break_not_zero = "x")