Add variable geom_hline to all facets of a barplot

Question

I have a barplot using the ggplot2 library:

plot <- qplot(Date, data=cns, 
              geom=\"bar\", binwidth = 1, 
              fill=Type, facets = N         


        

Answer 1

A variant on Didzis's answer, I would make a separate data frame for the summary data that you want to display per facet.

library("plyr")
cns.annotate <- ddply(cns, .(Name), summarize, y.int=mean(Days[Type=="Completed"]))

then pass this data frame to geom_hline.

qplot(Date, data=cns, 
      geom="bar", binwidth = 1, 
      fill=Type, facets = Name ~ .) +
  geom_hline(data=cns.annotate, aes(yintercept=y.int))

or in ggplot rather than qplot syntax:

ggplot(cns, aes(x=Date)) +
  geom_bar(aes(fill=Type), binwidth=1) +
  geom_hline(data=cns.annotate, aes(yintercept=y.int)) +
  facet_grid(Name ~ .)