library(ggplot2)
alpha <- 0.05 # a significance level
n <- 10       # degree of freedom
accept <- function(x){
  y <- dt(x, n)
  y[x < qt(alpha/2, n) | x > qt(1 - alpha/2, n)] <- NA
  return(y)
}
reject <- function(x){
  y <- dt(x, n)
  y[x > qt(alpha/2, n) & x < qt(1 - alpha/2, n)] <- NA
  return(y)
}
N <- 1e4 # a large number
s <- 5   # fontsize
p <-
  ggplot(data.frame(x=c(-3, +3)), aes(x=x)) +
  stat_function(
    fun=accept, geom="area",
    fill="#0072B2", n=N) + 
  stat_function(
    fun=reject, geom="area",
    fill="#D55E00", n=N) +
  annotate(
    "text", x=0, y=0.2, 
    parse=T, label="1-alpha", 
    size=s, colour="#EEEEEE") +  
  annotate(
    "text", x=-2.5, y=0.2, 
    parse=T, label="alpha/2", 
    size=s, colour="#D55E00") +
  annotate(
    "text", x=+2.5, y=0.2, 
    parse=T, label="alpha/2", 
    size=s, colour="#D55E00") +
  annotate(
    "text", x=qt(alpha/2, n), y=-0.02,
    parse=T, label="-t[n-1](alpha/2)",
    size=s, colour="#000000") +
  annotate(
    "text", x=0, y=-0.02,
    label="0",
    size=s, colour="#000000") +
  annotate(
    "text", x=qt(1 - alpha/2, n), y=-0.02,
    parse=T, label="+t[n-1](alpha/2)",
    size=s, colour="#000000") +
  theme(
    axis.text.y=element_blank(), 
    axis.text.x=element_blank(),
    axis.ticks=element_blank()) +
  labs(x="", y="")

svg(filename="confidence-interval.svg", width=16/2, height=9/2)
plot(p)
dev.off()