加截距线

library(dplyr)

## Error in `library()`:
## ! there is no package called 'dplyr'

library(tidyr)

## Error in `library()`:
## ! there is no package called 'tidyr'

library(ggplot2)

## Error in `library()`:
## ! there is no package called 'ggplot2'

  data_frame(
    x = rbinom(n = 1000, size = 10, prob = 0.7)
  ) %>%
  ggplot(aes(x = x)) + 
    geom_density() + 
geom_vline(aes(xintercept = 7, col = "red", alpha = 0.25))

## Error in `data_frame(x = rbinom(n = 1000, size = 10, prob = 0.7)) %>% ggplot(aes(x = x))`:
## ! could not find function "%>%"

其中geom_vline中的v是vertical的缩写，因此是垂直线，因此对应的水平线代码是geom_hline。