Annotations that work in ggplot2 3.1.1 fail in 3.2.1. How to fix?

Question

My code that makes custom annotations in faceted histograms in ggplot2 3.1.1 fails on a different computer running ggplot2 3.2.1, throws this error: Error: Aesthetics must be either length 1 or the same as the data (9): label

How can I make my annotations appear in the facets made in ggplot2 3.2.1?

Minimal example using mtcars follows.

Thank you!!

library(ggplot2, warn.conflicts = FALSE)
library(dplyr, warn.conflicts = FALSE)

lb <- mtcars %>%
      group_by(cyl) %>%
      summarize(n=n(), avg_gear=round(mean(gear),1))
lb$label <- paste0("n=",lb$n, "     avg_gear=",lb$avg_gear)
print(lb)

ggplot(data=mtcars, aes(x=gear)) +
geom_histogram(binwidth=1) +
facet_grid(. ~ cyl) +
annotate("text", x=4, y=13, label=lb$label) +  
ggtitle("histograms of gear, faceted by cyl") 

Answer 1

You might use another layer:

ggplot(data=mtcars, aes(x=gear)) +
  geom_histogram(binwidth=1) +
  facet_grid(. ~ cyl) +
  geom_text(data = lb, aes(x = 4, y = 13, label = label)) +    # in place of annotate
  ggtitle("histograms of gear, faceted by cyl")