I'm trying to make a pre-post change plot for three groups. In my data frame, pre data and post data are stored as two different variables like this.
pre_treat <- c(5,8,4,6,5,9,6,7,5)
post_treat <- c(2,2,4,10,9,11,4,5,3)
group <- c("A","A","A","B","B","B","C","C","C")
df <- data.frame(pre_treat = pre_treat,
post_treat = post_treat,
group = group)
> df
pre_treat post_treat group
1 5 2 A
2 8 2 A
3 4 4 A
4 6 10 B
5 5 9 B
6 9 11 B
7 6 4 C
8 7 5 C
9 5 3 C
I want to plot mean values of pre_treat and post_treat for each group like the image below. I also want to plot them with group facets.

