在 R 中，如何在不替换的情况下获取大小为 n 的样本，其中向量采样的长度为 <= n

Question

When I run the following I get an error:

sample(c(1,4),5,replace=FALSE)

This is the error:

  Error in sample.int(length(x), size, replace, prob) : 
  cannot take a sample larger than the population when 'replace = FALSE'

Is there a way to sample without replacement where it just automatically stops sampling once there is nothing left to sample? The result in this case I would like to be 1,4 or 4,1.

Answer 1

You can do it with an if else statement.

size_n <- 5
vec <- c(1, 4)

if (length(vec) < size_n) {
  sample(vec, length(vec), replace = F)
} else {
    sample(vec, size_n, replace = F)
  }

Answer 2

If we generalize the question in a way to "take sample size up to n" without replacement, we can do:

population <- c(1, 4)
samplesize_max <- 5

sample(population, min(length(population), samplesize_max), replace = FALSE)