在ggplot中的时间轴上轻推一个标签

Question

我想在ggplot中添加并轻推一个文本标签，但是当x是POSIXct类时，nudge_x不会改变任何内容，无论值是多少。示例代码：

library(ggplot2)

start.time <- c("7:00", "8:00", "9:30")
end.time <- c("10:00", "11:00", "13:30")
market <- c("Name1", "Name2", "Name3")

df <- data.frame(market, start.time, end.time)

df$start.time <- as.POSIXct(df$start.time, format="%H:%M")
df$end.time <- as.POSIXct(df$end.time, format="%H:%M")
df$length <- df$end.time - df$start.time


ggplot(df) +
  geom_segment(aes(x = start.time, xend = end.time, 
               y = market, yend = market), 
           color = "darkgreen", size = 2) +
  geom_text(aes(x = min(start.time), y = market, label = length), 
        hjust = 0, size = 3, color = "darkgreen", nudge_x = -1)

创建此图片：

我希望线条长度的标签更靠左边。我不认为nudge_x = -1正在注册，因为它不是正确的类。

谢谢！

Answer 1

在日期时间刻度上nudge_x = -1向左移动1秒，这是不可见的，可能是你要轻推1小时（3600秒）：

ggplot(df) +
  geom_segment(aes(x = start.time, xend = end.time, 
                   y = market, yend = market), 
               color = "darkgreen", size = 2) +
  geom_text(aes(x = min(start.time), y = market, label = length), 
            hjust = 0, size = 3, color = "darkgreen", nudge_x = -3600)

用15分钟轻推nudge_x = -15*60

Answer 2

作为另一种选择，您可以将标签放在细分中。例如：

library(dplyr)

ggplot(df) +
  geom_segment(aes(x = start.time, xend = end.time, 
                            y = market, yend = market), 
               color = "darkgreen", size = 5) +
  geom_text(data=df %>% group_by(market) %>% 
              summarise(xval=mean(c(end.time, start.time)),
                        length=paste(length, "hours")),
            aes(x = xval, y = market, label = length), 
            size = 3, color = "white") + 
  labs(x="Time") + theme_bw()