Adding multiple text annotations to a faceted ggplot geom_histogram - r

Question

I have the following data.frame:
hist.df <- data.frame(y = c(rnorm(30,1,1), rnorm(15), rnorm(30,0,1)),
gt = c(rep("ht", 30), rep("hm", 15), rep("hm", 30)),
group = c(rep("sc", 30), rep("am", 15), rep("sc",30)))
from which I produce the following faceted histogram ggplot:
main.plot <- ggplot(data = hist.df, aes(x = y)) +
geom_histogram(alpha=0.5, position="identity", binwidth = 2.5,
aes(fill = factor(gt))) +
facet_wrap(~group) +
scale_fill_manual(values = c("darkgreen","darkmagenta"),
labels = c("ht","hm"),
name = "gt",
limits=c(0, 30))
In addition, I have this data.frame:
text.df = data.frame(ci.lo = c(0.001,0.005,-10.1),
ci.hi = c(1.85,2.25,9.1),
group = c("am","sc","sc"),
factor = c("nu","nu","alpha"))
Which defines the text annotations I want to add to the faceted histograms, so that the final figure will be:
So text.df$ci.lo and text.df$ci.hi are confidence intervals on the corresponding text.df$factor and they correspond to the faceted histograms through text.df$group
Note that not every histogram has all text.df$factor's.
Ideally, the ylim's of the faceted histograms will leave enough space for the text to be added above the histograms so that they appear only on the background.
Any idea how to achieve this?

Answer 1

Wrapping my comment into an answer:
text.df$ci <- paste0(text.df$factor, ' = [', text.df$ci.lo, ', ', text.df$ci.hi, ']')
new_labels <- aggregate(text.df$ci, by = list(text.df$group),
FUN = function(x) paste(x, collapse = '\n'))$x
hist.df$group <- factor(hist.df$group)
hist.df$group <- factor(hist.df$group,
labels = paste0(levels(hist.df$group), '\n', new_labels))
main.plot <- ggplot(data = hist.df, aes(x = y)) +
geom_histogram(alpha=0.5, position="identity", binwidth = 2.5,
aes(fill = factor(gt))) +
facet_wrap(~group) +
scale_fill_manual(values = c("darkgreen","darkmagenta"),
labels = c("ht","hm"),
name = "gt")
main.plot + theme(strip.text = element_text(size=20))
If you wish to stick to the original idea, this question has an answer that will help.