错误提示：
Error in X[[floor(a * n) + 1]] : recursive indexing failed at level 2
In addition: Warning messages:
1: In (floor(a * n) + 1):(n - floor(a * n)) :
  numerical expression has 10000 elements: only the first used
2: In (floor(a * n) + 1):(n - floor(a * n)) :
  numerical expression has 10000 elements: only the first used

代码：函数略微复杂，


n <- 100
X <- list()
#生成X(1),...,X(n)
samples <- sample(1:(10*n), n)
order <- order(samples, decreasing=F)
for(i in 1:n){
  orderX[] <- samples[[order[]]]
}

#s^2(a)
s2 <- function(a){
  #m(α)
  sumX <- 0
  for(i in (floor(a*n)+1):(n-floor(a*n))){
    sumX <- sumX+X[]
  }
  m <- 1/(n-2*floor(a*n))*sumX
  #Var(a)
  VarX <- 0
  for(i in (floor(a*n)+1):(n-floor(a*n))){
    VarX <- VarX+(X[]-m)^2
  }
  VarX <- VarX/n
  result <- 1/(1-2*a)^2*(VarX+a*(X[[floor(a*n)+1]]-m)^2+a*(X[[n-floor(a*n)]]-m)^2)
}

# 利用curve函数进行绘制
curve(s2,from=0.1,to=0.4)