它不会读标题：

d_df %>%
  mutate ( Year = substr(Date, 7, 10)) %>% 
  mutate(Structures = ifelse(ID %in% tnnls, "tunnelS", "bridges")) %>%
  filter( Year %in% yrs_wnt)  %>% 
  group_by(Year, Structures) %>% 
  summarise( Total = sum(EZPass)+ sum(Cash)) %>%
  pivot_wider (names_from= Structures, values_from= Total) %>%
  mutate( Percentb = (bridges / (tunnels + bridges)))

字符串
这就是错误：
summarise()已按“Year”对输出进行分组。您可以使用.groups参数进行覆盖。
mutate()中的错误：在参数中出现错误：Percentb = (bridges/(tunnels + bridges))。在组1中出现错误：Year = "2012"
我以为会有另一个关于桥梁比例的专栏。