Adapted from this post (R graphics: Add labels to stacked bar chart)
For inside labels:
teachers <- c("A", "B","C", "D", "E")
mean_pre_scores <- c(10, 11, 12, 10,9)
mean_post_scores <- c(12,15,17,13,12)
pre_post.df <- data.frame(mean_pre_scores, mean_post_scores)
pre_post <- as.matrix(pre_post.df)
b<-barplot((t(pre_post)), beside = T, names = teachers, legend = c("pre", "post"),
ylim = c(0,20), args.legend = list(x="bottomright"), axes = T, main = "Unit 1 Content Pre Test",
col=c(26,51))
ypos.inside<-apply(pre_post, 2, function(x) x -1 )
ypos.inside <- t(ypos.inside)
text(b, ypos.inside, pre_post)
For outside labels:
teachers <- c("A", "B","C", "D", "E")
mean_pre_scores <- c(10, 11, 12, 10,9)
mean_post_scores <- c(12,15,17,13,12)
pre_post.df <- data.frame(mean_pre_scores, mean_post_scores)
pre_post <- as.matrix(pre_post.df)
b<-barplot((t(pre_post)), beside = T, names = teachers, legend = c("pre", "post"),
ylim = c(0,20), args.legend = list(x="bottomright"), axes = T, main = "Unit 1 Content Pre Test",
col=c(26,51))
ypos.outside<-apply(pre_post, 2, function(x) x +1 )
ypos.outside <- t(ypos.outside)
text(b, ypos.outside, pre_post)