将垂直线添加到日期x轴

Question

我有下面的情节，我想在“11:20:33”

添加一条垂直线

我试图使用：geom_vline（aes（xintercept =“11:20:33”））

但这似乎不起作用。有什么想法吗？

library(scales)
    library(ggplot2)
     time = as.POSIXct(c("2016-06-30 15:20:23 GMT","2016-06-30 15:20:25 GMT","2016-06-30 15:20:27 GMT","2016-06-30 15:20:29 GMT","2016-06-30 15:20:35 GMT"),tz = "GMT")
     attr(time, "tzone") <- "America/New_York"
     class(time)
     value = c(10,NA,0, 5, 0)
     category = c(0,0,0,0,0)
     dat = data.frame(t = time, value = value, category = category)
     dat
     str(dat)

     ggplot(dat, aes(x=t, y = value, group = 1 )) +
       geom_point(aes (color = as.factor(category)) ) +geom_line()  +
       geom_vline(aes(xintercept =  "11:20:33" ))  +
       scale_x_datetime(date_labels = "%H:%M:%S")+  theme(axis.text.x = element_text(angle = 90, hjust = 1, size = 7))