Final exams

library(tidyverse)

## -- Attaching packages --------------------------------------- tidyverse 1.3.1 --

## v ggplot2 3.3.5     v purrr   0.3.4
## v tibble  3.1.6     v dplyr   1.0.8
## v tidyr   1.2.0     v stringr 1.4.0
## v readr   2.1.2     v forcats 0.5.1

## Warning: 程辑包'stringr'是用R版本4.1.3 来建造的

## -- Conflicts ------------------------------------------ tidyverse_conflicts() --
## x dplyr::filter() masks stats::filter()
## x dplyr::lag()    masks stats::lag()

 best_in_class <- mpg %>%
      group_by(class) %>%
      filter(row_number(desc(hwy)) == 1)
    ggplot(mpg, aes(displ, hwy)) +
      geom_point(aes(color = class)) +
      geom_text(aes(label = model), data = best_in_class)