15.3 t-분포 (t-Distribution) : stat_function(fun = dt)

# t-분포 : fun = dt 
ggplot(data.frame(x=c(-3,3)), aes(x=x)) +
       stat_function(fun=dt, args=list(df=2), colour="red", size=2) +
       ggtitle("t-Distribution of df=2")