如何用注释在ggplot2中绘制箭头 [英] how to draw arrow in ggplot2 with annotation

问题描述

我正在创建一个ggplot图表，我需要添加一些注释。我可以做到这一点，但文字并不完全指向我喜欢注释的日期。有没有一种方法可以绘制箭头到axix，我喜欢创建注释。

I am creating a ggplot chart where I need to put some annotation. I can do that but the text is not really pointing exactly the date that I like annotate. Is there a way to draw an arrow to axix where I like create the annotation.

我有这个：

I have this:

   ggplot(df, aes(Date, CPU)) + geom_point() + 
       annotate("text", x = as.POSIXct(c("2013-03-11 23:00:00")), 
                y = 90, label = "problem 1", angle=90, size=5, 
                colour='black', face="bold")

推荐答案

正因如此，任何人都可能有相同的问题或查询，下面是我做了：

just so anyone might have the same question or query, here is what I did:

library(ggplot2)
library(grid)

ggplot(df, aes(Date, CPU)) + geom_point() + 
       annotate("text", x = as.POSIXct(c("2013-03-11 23:00:00")), 
                y = 90, label = "problem 1", angle=90, size=5, 
                colour='black', face="bold")
             +    geom_segment(aes(x = as.POSIXct(c("2013-03-11 09:00:00")), y = -30, xend = as.POSIXct(c("2013-03-11 09:00:00")), yend = 0), colour='#CC00FF', size=1,arrow = arrow(length = unit(0.5, "cm")))

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