简述：
Sample函数从xextracts a sample of the specified size from the elements of,with or without replacement.
其使用格式为：

sample函数

sample(x, size, replace = FALSE, prob = NULL)

其中：

• x：A selection of one or more elements of the vector,或一个正整数
• n：一个正数,Number of items to choose from.
• size：一个非负整数,Indicates the number of items available for selection
• replace：Sampling should be replaced
• prob：vector of probability weights used to obtain the elements of the sampled vector.
  举例：

x <- 1:12
sample(x)

从1-12随机抽取12个元素,Equivalent to no back sample

sample(x,replace=T)

The output has duplicate values,Equivalent to sampling with replacement

y <- c(0,1) 
sample(y,100,replace=T)

这里的100就是抽取100个元素,Because we're sampling with replacement here,So you can draw countless times
其他用法：

• Conditional extraction
  比如抽取1到10中大于5的样本

sample(x[x >  5]) 

大于10的样本（Obviously one doesn't）

sample(x[x > 10])

输出整数0

但是注意！！！when you want output greater than9的样本的时候（很明显只有10）
Rlanguage is output10个向量.这也是需要注意的一点

sample(x[x > 9])

If you really want to start from greater than9If extracted from the number of,需要使用sample.int函数

resample <- function(x, ...) x[sample.int(length(x), ...)]
resample(x[x >  8]) # length 2
resample(x[x >  9]) # length 1
resample(x[x > 10]) # length 0

The output is normal

sample.int函数

比如我想从1到1000randomly selected from time to time50个整数,有放回的抽样（可重复抽样）

sample.int(1e3, 100)

1e3代表1000,1en代表10的n次方