Annotate outside plot area once in ggplot with facets

Question

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?

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")

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

How can I get this to only appear once?

It's an argument to the latest v 3.1 also: https://ggplot2.tidyverse.org/reference/coord_cartesian.html — Scransom, Nov 06 '18 at 07:56
Maybe try [cowplot](https://cran.r-project.org/web/packages/cowplot/vignettes/introduction.html) for annotation. — zx8754, Nov 06 '18 at 08:01
[geom_text](https://stackoverflow.com/a/53027319/786542) works too — Tung, Nov 06 '18 at 08:25
@Tung I've tried some geom_text options, including your link, but I can't get anything to work or even plot off the plot area — Scransom, Nov 06 '18 at 08:35
@Umaomamaomao: works for me with the latest `ggplot 2 v3.1.0` — Tung, Nov 06 '18 at 15:42

score 10 · Accepted Answer · answered Nov 06 '18 at 18:50

10

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")

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))

answered Nov 06 '18 at 18:50

aosmith

34,856
9
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Note that while all answers here produce the desired result, this one seems the most direct, which is why I've accepted – Scransom Nov 06 '18 at 23:27
hi, thanks for the answer -- however, I get this error: `"plot.tag.position" is not a valid theme element name.` – jjrr Nov 27 '18 at 15:23
1

@jjrr I believe this was [introduced in ggplot2_3.0.0](https://github.com/tidyverse/ggplot2/blob/master/NEWS.md#new-features-1). I am currently using ggplot2_3.1.0 and `plot.tag.position` is working fine for me in `theme()`. – aosmith Nov 27 '18 at 15:29
yeah, sorry -- I just realised indeed I was on a older v – jjrr Nov 27 '18 at 15:49
I run the codes and get this error: Error in coord_cartesian(xlim = c(50, 350), ylim = c(10, 35), clip = "off") : unused argument (clip = "off"). I don't know why. @aosmith – Revo May 20 '19 at 12:47
I can't reproduce the error message in **ggplot2** version 3.1.1, @Revo. What version of **ggplot2** are you using? – aosmith May 20 '19 at 14:16

score 3 · Answer 2 · answered Nov 06 '18 at 08:11

3

It's in fact very easy, just have a vector of labels, where the ones you don't want to plot are the empty string "".

library("ggplot2")

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

answered Nov 06 '18 at 08:11

Rui Barradas

70,273
8
34
66

1

Ahh yes, the old bait-and-switch – Scransom Nov 06 '18 at 08:26
1

@Umaomamaomao I tried the same with `geom_text` and it doesn't work, afaik, it must be `annotate`. – Rui Barradas Nov 06 '18 at 08:28

score 3 · Answer 3 · answered Jan 14 '19 at 21:58

Alternatively, the package cowplot has the handy annotation function draw_label(). When used in combination with ggdraw(), can annotate anywhere on the canvas/sheet with the coordinates ranging from 0 to 1 (relative to the entire canvas). The function cowplot::draw_label() uses ggplot2::annotation_custom() under the hood.

library(ggplot2)
library(cowplot)
#> Warning: package 'cowplot' was built under R version 3.5.2
#> 
#> Attaching package: 'cowplot'
#> The following object is masked from 'package:ggplot2':
#> 
#>     ggsave

# Revert to default theme; see https://stackoverflow.com/a/41096936/5193830
theme_set(theme_grey())

p <- ggplot(mtcars, aes(x = hp, y = mpg)) +
  geom_point() +
  facet_grid(. ~ cyl)

ggdraw(p) + draw_label("XX", x = 0.02, y = 0.97)

^{Created on 2019-01-14 by the reprex package (v0.2.1)}

score 2 · Answer 4 · edited Nov 07 '18 at 08:46

2

With geom_text:

dummy <- data.frame(cyl = c(4), l = c("XX"), stringsAsFactors = F)

ggplot(mtcars, aes(x = hp, y = mpg)) +
  geom_point() +
  geom_text(data=dummy, aes(label=l), x = -20, y = 36) +
  facet_grid(.~cyl ) + 
  coord_cartesian(xlim = c(50, 350), ylim = c(10, 35), clip = "off")

edited Nov 07 '18 at 08:46

Scransom

3,175
3
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answered Nov 06 '18 at 18:48

user10614886

21
1

Welcome to stackoverflow and thanks for contributing :-) So then `geom_text` works ? Please consider adding a picture showing the results like in the other answers. – Gabriel Devillers Nov 06 '18 at 18:59
@GabrielDevillers I don't think new users can add images, which is a bit silly - I always forget what "privileges" who has – Scransom Nov 06 '18 at 23:18

Annotate outside plot area once in ggplot with facets

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