用均值向量调用 rnorm [英] Calling rnorm with a vector of means

问题描述

当我调用 rnorm 传递单个值作为平均值时，很明显会发生什么:一个值是从 Normal(10,1) 生成的.

When I call rnorm passing a single value as mean, it's obvious what happens: a value is generated from Normal(10,1).

y <- rnorm(20, mean=10, sd=1)

但是，我看到了整个向量被传递给 rnorm(或 rcauchy 等)的例子；在这种情况下，我不确定 R 机器的真正作用.例如:

But, I see examples of a whole vector being passed to rnorm (or rcauchy, etc..); in this case, I am not sure what the R machinery really does. For example:

a = c(10,22,33,44,5,10,30,22,100,45,97)
y <- rnorm(a, mean=a, sd=1)

有什么想法吗?

推荐答案

rnorm 生成的随机数的数量等于 a 的长度.来自 ?norm:

The number of random numbers rnorm generates equals the length of a. From ?rnorm:

n:观察次数.如果‘length(n) > 1’，取长度成为所需的数字.

n: number of observations. If ‘length(n) > 1’, the length is taken to be the number required.

要查看将 a 传递给 mean 参数时发生了什么，如果我们更改示例会更容易:

To see what is happening when a is passed to the mean argument, it's easier if we change the example:

a = c(0, 10, 100)
y = rnorm(a, mean=a, sd=1)
[1] -0.4853138  9.3630421 99.7536461

所以我们生成 length(a) 个均值 a[i] 的随机数.

So we generate length(a) random numbers with mean a[i].

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