Adding points to ends of lines

example.R

library(dplyr)
library(ggplot2)

# Create data
tibble(
  g = rep(c('A','B'), each = 50),
  z = rnorm(length(g))
  ) |>
  group_by(g) |>
  mutate(
    y = cumsum(z),
    x = row_number() + g %in% 'B' # offset a bit
    ) %>%
  ungroup() -> tbl

tbl |>
  ggplot(aes(x=x,y=y,group=g,color=g)) + 
  geom_line() +
  geom_point(
    data = tbl %>%
      group_by(g) %>%
      filter(x %in% range(x))
    )