How to insert annotation on the very top facet of ggplot in R?

Question

I would like to have the annotation on the very first facet of the following ggplot. right now, the code draws annotation on all facets. Anyway forward would be appreciate.

library(ggplot2)
library(lubridate)

set.seed(123)

DF <- data.frame(Date = seq(as.Date("2001-01-01"), to = as.Date("2005-12-31"), by = "1 month"),
                  Ob = runif(60,1,5), L95 =runif(60, 0,4), U95 = runif(60,2,7), Sim = runif(60,1,5)) %>% 
      pivot_longer(names_to = "Variable", values_to = "Value", -Date)

ggplot(data = DF, aes(x = Date))+
  geom_line(aes(y = Value))+
  facet_wrap(~ Variable, scales = "free_y", nrow = 4)+
  geom_vline(xintercept = as.Date("2004-12-01"),color = "red", size = 1.30)+
  annotate(geom = "text", x = as.Date("2002-01-01"), y = 3, label = "Calibration")+
  annotate(geom = "text", x = as.Date("2005-06-01"), y = 3, label = "Validation")

Duck · Answer 1 · 2020-11-23T13:16:20.787

1

You can try something like this wrapping data coordinates for the value on top of facets using geom_text():

library(ggplot2)
library(lubridate)
#Code
ggplot(data = DF, aes(x = Date))+
  geom_line(aes(y = Value,group=Variable))+
  facet_wrap(~ Variable, scales = "free_y", nrow = 4)+
  geom_vline(xintercept = as.Date("2004-12-01"),color = "red", size = 1.30)+
  geom_text(data=data.frame(Variable='L95',Date=as.Date("2002-01-01"),
                            label="Calibration",Value=max(DF$Value)),
            aes(y=Value,label=label))+
  geom_text(data=data.frame(Variable='L95',Date=as.Date("2005-06-01"),
                            label="Validation",Value=max(DF$Value)),
            aes(y=Value,label=label))

Output:

edited Nov 23 '20 at 13:16

answered Nov 23 '20 at 01:05

Duck

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thanks @Duck, i want the `annotation` on the first `facet` not on all `facets`. right now the code draws `annotation` on all four `facets`. The `calibration` and `validation` text should be displayed on the very top `facet`. – Hydro Nov 23 '20 at 01:10
@Hydro Hi dear. Deeply sorry for misunderstanding the task. I thought you wanted labels on top of each facet. Now, I have updated the post. Hoping that can be useful for you! – Duck Nov 23 '20 at 13:17

score 1 · Accepted Answer · answered Nov 23 '20 at 01:55

You can do this with geom_text. Create a separate dataframe for plotting.

library(ggplot2)

text_data <- data.frame(x = as.Date(c("2002-01-01", "2005-06-01")), 
                        y = 3.5, Variable = sort(unique(DF$Variable))[1], 
                        label = c("Calibration", "Validation"))

ggplot(data = DF, aes(x = Date))+
  geom_line(aes(y = Value))+
  facet_wrap(~ Variable, scales = "free_y", nrow = 4)+
  geom_vline(xintercept = as.Date("2004-12-01"),color = "red", size = 1.30) + 
  geom_text(data = text_data, aes(x, y, label = label), color = 'blue')

Hi @Ronak, can you please look into this question? https://stackoverflow.com/questions/64970528/annotation-on-only-the-first-facet-of-ggplot-in-r. Thanks — Hydro, Nov 23 '20 at 14:40

How to insert annotation on the very top facet of ggplot in R?

2 Answers2