是否可以使用n元素创建一个大小为x的样本的方法，该元素至少会出现x个元素n >= length(x) ？
示例：
> n = 10 # size of the sample
> vector <- c("a", "b", "c", "d") #
> sample(vector, size = n, replace = TRUE) #
[1] "b" "c" "b" "d" "b" "d" "c" "d" "c" "d" # "a", by chance, don't get selected
我希望每个元素至少出现一次，怎么可能？我应该使用其他功能吗？
输出示例：
> "a" "b" "b" "b" "c" "c" "c" "c" "c" "d"
> "c" "c" "a" "c" "d" "c" "c" "c" "b" "d"
> "a" "b" "c" "d" "a" "a" "a" "a" "a" "a"