How to annotate different values for each facet (bar plot) on R?

Question

I\'d like to know how to annotate each facet in my bar plot. Right now, I\'m using the geom_signif function which works perfectly except that it duplicates the annotation on

Answer 1

Here is an example of to do it by manually deconstructing the plot and reconstructing with new annotations. I understood it as you wanted manual text annotations per plot. This (very manual) solution is based on another answer, How do I annotate p-values onto a faceted bar plots on R?, which might be exactly what you are looking for.

df <- data.frame(iris,type = c(1,2))

## Construct your plot exactly as you have already done
## Annotations are replicated.
myplot <- ggplot(df, aes(x=Species,y = Sepal.Length)) + 
    geom_boxplot() + 
    facet_grid(.~type) + 
    geom_signif(annotation = c("foo"),xmin = 1, xmax = 2,y_position = 7.5)
myplot

## Disassemble plot
myplot2 <- ggplot_build(myplot)
myplot2$data[[2]]

 x xend     y  yend annotation group PANEL shape colour textsize angle hjust vjust alpha family fontface lineheight
1 1    1 7.392 7.500        foo     1     1    19  black     3.88     0   0.5     0    NA               1        1.2
2 1    2 7.500 7.500        foo     1     1    19  black     3.88     0   0.5     0    NA               1        1.2
3 2    2 7.500 7.392        foo     1     1    19  black     3.88     0   0.5     0    NA               1        1.2
4 1    1 7.392 7.500        bar     1     2    19  black     3.88     0   0.5     0    NA               1        1.2
5 1    2 7.500 7.500        bar     1     2    19  black     3.88     0   0.5     0    NA               1        1.2
6 2    2 7.500 7.392        bar     1     2    19  black     3.88     0   0.5     0    NA               1        1.2
  linetype size
1        1  0.5
2        1  0.5
3        1  0.5
4        1  0.5
5        1  0.5
6        1  0.5

## Note there are 6 observations, 3 for each "PANEL". 
## Now, change the annotation on each "PANEL".
myplot2$data[[2]]$annotation <- c(rep("foo",3),rep("bar",3))

## Reconstruct plot
myplot3 <- ggplot_gtable(myplot2)
plot(myplot3)