使用小平面在ggplot中注释一次绘图外部区域 [英] Annotate outside plot area once in ggplot with facets

问题描述

我想在多面ggplot中的绘图区域之外添加注释.我可以获得所需的注释，但是每个方面都会重复该注释.如何使该注释仅显示一次?

I want to add an annotation outside the plotting area in a faceted ggplot. I can get the annotation that I want, but it's repeated for each facet. How can I get this annotation to appear only once?

例如，要在左上角注释一次"XX"，我可以使用:

E.g., to annotate "XX" once in the top left hand corner I can use:

library("ggplot2")
ggplot(mtcars, aes(x = hp, y = mpg)) +
  geom_point() +
  facet_grid(.~cyl ) + 
  annotate("text", x = -20, y = 36, label = "XX") +
  coord_cartesian(xlim = c(50, 350), ylim = c(10, 35), clip = "off")

但这实际上将其注释在每个构面的左上方.

However this actually annotates it to the top left of each facet.

如何使它只出现一次?

推荐答案

您可以使用labs()中的tag在图形上放置单个标签标签.

You can put a single tag label on a graph using tag in labs().

ggplot(mtcars, aes(x = hp, y = mpg)) +
     geom_point() +
     facet_grid(.~cyl ) + 
     labs(tag = "XX") +
     coord_cartesian(xlim = c(50, 350), ylim = c(10, 35), clip = "off")

不过，该默认设置为左上"，这可能不是您想要的.您可以使用主题元素plot.tag.position来移动它，或者作为坐标(在绘图空间中介于0和1之间)或像"topright"这样的字符串.

This defaults to "top left", though, which may not be what you want. You can move it around with the theme element plot.tag.position, either as coordinates (between 0 and 1 to be in plot space) or as a string like "topright".

ggplot(mtcars, aes(x = hp, y = mpg)) +
     geom_point() +
     facet_grid(.~cyl ) + 
     labs(tag = "XX") +
     coord_cartesian(xlim = c(50, 350), ylim = c(10, 35), clip = "off") +
     theme(plot.tag.position = c(.01, .95))

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