如何使用图例在ggplot2中创建分段图？

我有如下数据：

我想创建一个分段图（例如前图和后图，包括在t = 10处的垂直线，以指示变化。t指的是经过的时间，x前执行指0，后执行指1实施，count_visit_triage\\d是我想在y轴上绘制的计数数据。

这是我的R代码。我将多个拼凑geom_smooth成一个数字，每种颜色代表的值triage1，triage2等等。因此，我无法获得图例。我的问题是（1）如何简化此代码，以便图例可以包含在图中？

ggplot(df, aes(x = t, y = count_visit_triage1)) +
  geom_smooth(data = subset(df, x == 0), aes(x = t, y = count_visit_triage1), colour = "blue", se = F) +
  geom_smooth(data = subset(df, x == 1), aes(x = t, y = count_visit_triage1), colour = "blue", se = F) +
  geom_smooth(data = subset(df, x == 0), aes(x = t, y = count_visit_triage2), colour = "orange", se = F) +
  geom_smooth(data = subset(df, x == 1), aes(x = t, y = count_visit_triage2), colour = "orange", se = F) +
  geom_smooth(data = subset(df, x == 0), aes(x = t, y = count_visit_triage3), colour = "green", se = F) +
  geom_smooth(data = subset(df, x == 1), aes(x = t, y = count_visit_triage3), colour = "green", se = F) +
  geom_smooth(data = subset(df, x == 0), aes(x = t, y = count_visit_triage4), colour = "red", se = F) +
  geom_smooth(data = subset(df, x == 1), aes(x = t, y = count_visit_triage4), colour = "red", se = F) +
  geom_vline(xintercept = 10, linetype = "dashed") + 
  theme_bw()

资料：

df <- structure(list(t = 1:20, x = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 
0L, 0L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), count_visit_triage1 = c(42L, 
55L, 61L, 52L, 58L, 38L, 47L, 46L, 66L, 44L, 24L, 17L, 40L, 25L, 
18L, 23L, 34L, 35L, 22L, 23L), count_visit_triage2 = c(175L, 
241L, 196L, 213L, 189L, 163L, 181L, 166L, 229L, 224L, 153L, 139L, 
125L, 145L, 134L, 115L, 152L, 153L, 136L, 154L), count_visit_triage3 = c(120L, 
114L, 106L, 88L, 108L, 103L, 103L, 93L, 80L, 81L, 88L, 94L, 94L, 
77L, 91L, 100L, 93L, 70L, 79L, 77L), count_visit_triage4 = c(3L, 
0L, 0L, 1L, 2L, 2L, 0L, 4L, 4L, 2L, 0L, 0L, 0L, 0L, 0L, 1L, 0L, 
0L, 1L, 2L)), row.names = c(NA, -20L), class = c("tbl_df", "tbl", 
"data.frame"))