Annotate a point for different facet plots

Question

I want to annote a point onto a bar-plot for each independent facet plot. However, when I use annotate it annotates both plots simultaneously at the same points. How can I specify a point annotation different to each plot?

Here's my data and code:

data = structure(list(training = c("NBack", "NBack", "NBack", "NBack", 
"NBack", "NBack", "NBack", "NBack", "NBack", "NBack", "NBack", 
"Speed", "Speed", "Speed", "Speed", "Speed", "Speed", "Speed", 
"Speed", "Speed", "Speed"), Scores = c(1, 3, 4, 4, 0, 1, -4, 
-1, -2, 1, 2, 3, -3, -1, 1, 1, -4, -2, 3, -2, 3)), row.names = c(NA, 
-21L), class = c("tbl_df", "tbl", "data.frame"))

ggplot(data, aes(x = scores, colour = factor(training),
       stat="identity")) +  
geom_bar(fill="white") + 
 facet_wrap(~training, scales="free_x") + 
 labs(colour='Training', x="Score differences", y = "Frequency of    differences") + 
 annotate("point", x = 1, y = 4,  size = 2, colour = "black") 

Answer 1

Just add another geom_point with another table containinga nnotation coordinates:

library(tidyverse)

data <- structure(list(training = c(
  "NBack", "NBack", "NBack", "NBack",
  "NBack", "NBack", "NBack", "NBack", "NBack", "NBack", "NBack",
  "Speed", "Speed", "Speed", "Speed", "Speed", "Speed", "Speed",
  "Speed", "Speed", "Speed"
), Scores = c(
  1, 3, 4, 4, 0, 1, -4,
  -1, -2, 1, 2, 3, -3, -1, 1, 1, -4, -2, 3, -2, 3
)), row.names = c(
  NA,
  -21L
), class = c("tbl_df", "tbl", "data.frame"))

annotations <- tribble(
  ~training, ~Scores, ~y,
  "NBack", 1, 4,
  "Speed", 2, 5,
)

ggplot(data, aes(
  x = Scores, colour = factor(training),
  stat = "identity"
)) +
  geom_bar(fill = "white") +
  geom_point(
    data = annotations,
    mapping = aes(y = y), # add lacking aesthetics
    color = "black",
    size = 3
  ) +
  facet_wrap(~training, scales = "free_x") +
  labs(
   colour = "Training", x = "Score differences",
   y = "Frequency of    differences"
  )