用于替换向量值的 For 循环

Question

我不知道我的代码有什么问题。基本上我正在尝试做一个小版本的 Monte Carlo 模拟。

这是我的输入

mydata=[1,4,20,23,37]
prediction=c(0,0,0,0,0,0,0,0,0,0,0,0)
randomvar=runif(12,0,1)

然后我有这个条件：

if i-th value of randomvar is > 0.97, replace i-th value of prediction with 5th data from mydata

else if i-th value of randomvar is > 0.93, replace i-th value of prediction with 4th data from mydata

else if i-th value of randomvar is > 0.89, replace i-th value of prediction with 3rd data from mydata

else if i-th value of randomvar is > 0.85, replace i-th value of prediction with 2nd data from mydata

else if i-th value of randomvar is > 0.81, replace i-th value of prediction with 1st data from mydata

else 0

所以我写了这个：

mydata=c(1,4,20,23,37)
prediction=c(0,0,0,0,0,0,0,0,0,0,0,0)
random=runif(12,0,1)
for (i in random) {
  if (i>0.97) prediction[i]=mydata[5]
  else if (i>0.93) prediction[i]=mydata[4]
  else if (i>0.89) prediction[i]=mydata[3]
  else if (i>0.85) prediction[i]=mydata[2]
  else if (i>0.81) prediction[i]=mydata[1]
  else prediction[i]=0
}
prediction

结果是

> prediction
 [1] 0 0 0 0 0 0 0 0 0 0 0 0

我想知道为什么代码不会根据上述条件更改预测值。谁能帮忙解释一下为什么？反正我是 R 的新手

Answer 1

代码无效，因为使用 runif 生成的随机值不是整数。

> random=runif(12,0,1)
> random
 [1] 0.78381826 0.97424261 0.87240491 0.20896106 0.95598721 0.11609102 0.02430861
 [8] 0.24213124 0.45808710 0.28205870 0.51469212 0.02672362

现在 prediction[i] i 在 random 中是没有意义的。

去做 --

for (i in seq_along(random)) {
  if (random[i]>0.97) prediction[i]=mydata[5]
  else if (random[i]>0.93) prediction[i]=mydata[4]
  else if (random[i]>0.89) prediction[i]=mydata[3]
  else if (random[i]>0.85) prediction[i]=mydata[2]
  else if (random[i]>0.81) prediction[i]=mydata[1]
  else prediction[i]=0
}
prediction
> prediction
 [1]  0  0  0  0 20  4  0  0  0  0  0  0

用于替换向量值的 For 循环

A For loop to replace vector value

for-loop

if-statement

r

montecarlo