在R中生成数字 [英] Generate numbers in R

问题描述

在R中，如何生成平均值为X，中位数为Y(至少接近)的N个数字.

In R, how can I generate N numbers that have a mean of X and a median of Y (at least close to).

或更一般地说，是否有一种算法?

Or perhaps more generally, is there an algorithm for this?

推荐答案

有无数种解决方案.

近似算法:

1. 在中位数以下生成n/2个数字
2. 在中位数上方生成n/2个数字
3. 添加所需的中位数并检查
4. 添加一个权重足以满足您的均值的数字-您可以解决

假设您希望中位数为零且平均值为20的示例:

Example assuming you want a median of zero and a mean of twenty:

R> set.seed(42)
R> lo <- rnorm(10, -10); hi <- rnorm(10, 10)
R> median(c(lo,0,hi))
[1] 0                         # this meets our first criterion
R> 22*20 - sum(c(lo,0,hi))    # (n+1)*desiredMean - currentSum
[1] 436.162                   # so if we insert this, we the right answer
R> mean(c(lo,0,hi,22*20 - sum(c(lo,0,hi))))
[1] 20                        # so we meet criterion two
R> 

因为desiredMean times (n+1)必须等于sum(currentSet) + x，所以我们解决了x得到上面的表达式.

because desiredMean times (n+1) has to be equal to sum(currentSet) + x so we solve for x getting the expression above.

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