How can I add a subtitle and change the font size of ggplot plots in R?

Question

I tried adding a subtitle using +opts(subtitle=\"text\") but nothing showed up. The main title does work (+opts(title=\"text\")).

I would also

Answer 1

Update: ggplot version 2.2.0 can do subtitles, as demonstrated e.g. in this blog post.

Example:

library(ggplot2)
packageVersion("ggplot2")  ## 2.2.0
d <- data.frame(x=1:5,y=1:5)
ggplot(d,aes(x,y))+
    labs(title="abc",subtitle="def")+
    ## default left-aligned: moved them to center alignment
    theme(plot.title=element_text(hjust=0.5),
          plot.subtitle=element_text(hjust=0.5))