R中的Excel目标搜索 [英] Excel Goal seek in R

问题描述

我已经使用excel目标搜索功能计算了所需的安全库存.下面是图像. 但是现在我想使用R来做同样的事情.

I have calculated the required Safety Stock using the excel goal seek function. Below is the image. But now I want to do the same using R.

当我输入SafetyStock&时，以下功能会给我相同的excel结果.标清现在，我需要进行反向计算(每当我提供x& SD时，我就需要SS).有人可以帮我吗?

The below function gives me the same excel results when I enter the SafetyStock & SD. Now I need to do the reverse calculation(Whenever I provide x & SD I need the SS). Could someone help me with the same?

我尝试了Optix和其他类似的R包，但没有成功.

I tried Optix and other similar R packages but couldn't succeed.

opt<-function(SS,SD){

  x=-SS*(1-pnorm(SS/SD)) + SD * dnorm(SS/SD,mean=0,sd =1,0)
  print(x)

}

Excel目标搜索

推荐答案

为x求解f(x)=c与解决f(x)-c=0相同.您可以使用uniroot来找到根:

Solving f(x)=c for x is the same as solving f(x)-c=0. You can use uniroot to find the root:

f <- function(SS, SD, ESC) {
  -SS*(1-pnorm(SS/SD)) + SD * dnorm(SS/SD,mean=0,sd =1,0) - ESC
}

zero <- uniroot(f,c(0,1000),SD=600,ESC=39.3)
zero$root

第二个参数是搜索间隔:0到1000.返回

The second argument is the interval to search: between 0 and 1000. This returns

674.0586 

zero结构具有更多有趣的信息:

The zero structure has more interesting information:

$root
[1] 674.0586

$f.root
[1] 1.933248e-08

$iter
[1] 8

$init.it
[1] NA

$estim.prec
[1] 6.103516e-05

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