如何从R中的随机数生成器指定奇数和偶数的数量？

Question

I need to generate a random selection of 9 whole numbers from 1 to 40 with the following condition: the output must contain 5 even numbers and 4 odd numbers.

I have the following code to generate 9 random numbers:

x1<- sample(1:40, 9, replace=F)
> x1
  [1]  2 36  6 10 39 17 14 11 25

I now need to add the odd and even numbers condition in the equation. How can I do this?

Answer 1

Assuming the order of the numbers does not matter, you could try

c(sample(seq(2,40,by=2), 5, replace=F), sample(seq(1,39,by=2), 4, replace=F))

where seq(2,40,by=2) generates the even numbers, and seq(1,39,by=2) generates the odd numbers. If the order does matter (ie it should also be random), you can wrap the outer c with sample :

sample(c(sample(seq(2,40,by=2), 5, replace=F),sample(seq(1,39,by=2), 4, replace=F)))

Hope this helps!

Answer 2

您可以尝试以下方法：

sample(c(2*sample(0:19, 4) + 1, 2*sample(1:20, 5)))