来自不同长度向量的样本(包括 1 个) [英] Sample from vector of varying length (including 1)

问题描述

我有一个长度可变的向量，有时长度为 1.

I have a vector with varying length, which can sometimes be of length 1.

我想从这个向量中采样，如果它的长度是 1，它总是采样那个 1 个数字.

I would like to sample from this vector such that if its length is 1 it always samples that 1 number.

sample() 不会这样做，因为当样本大小为 1 时，它会从 1 到数字进行采样.

sample() won't do this because it samples from 1 to the digit when sample size is 1.

推荐答案

这是一个文档化的功能:

This is a documented feature:

如果 x 的长度为 1，则为 numeric(在 is.numeric 的意义上)和 x >= 1，从1:x开始采样.请注意，当 x 在诸如 sample(x) 之类的调用中具有不同的长度时，此便利功能可能会导致不良行为.

If x has length 1, is numeric (in the sense of is.numeric) and x >= 1, sampling via sample takes place from 1:x. Note that this convenience feature may lead to undesired behaviour when x is of varying length in calls such as sample(x).

另一种方法是编写自己的函数来避免该功能:

An alternative is to write your own function to avoid the feature:

sample.vec <- function(x, ...) x[sample(length(x), ...)]
sample.vec(10)
# [1] 10
sample.vec(10, 3, replace = TRUE)
# [1] 10 10 10

一些具有类似行为的函数列在 seq 与 seq_along.什么时候使用 seq 会导致意想不到的结果?

Some functions with similar behavior are listed under seq vs seq_along. When will using seq cause unintended results?

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