Joining means on a boxplot with a line (ggplot2)

Question

I have a boxplot showing multiple boxes. I want to connect the mean for each box together with a line. The boxplot does not display the mean by default, instead the middle

Answer 1

Another longer approach (in case if the data is in two different dataframes) is:

library(dplyr); library(ggplot2)

x <- factor(rep(1:10, 100)); y <- rnorm(1000);
df <- data.frame(x=x, y=y);
df_for_line <- group_by(x) %>% summarise(mean_y = mean(y));
ggplot(df, aes(x = x, y = y)) + geom_boxplot() + 
   geom_path(data = df_for_line, aes(x = x, y = mean_y, group = 1))

Again, group = 1 is the key.