将答案从函数存储到R中的向量中 [英] Storing Answers From Functions into a Vector in R

问题描述

系统提示我一个问题，而且离解决我所需要的一切都非常接近.问题如下-

编写一个while循环，该循环将在每次支撑代码重复时将mynu​​m减1，从而将任何非负整数mynum的阶乘计算并存储为新对象.

另一个因素是，如果输入0或1，则输出将为1.

我编写的代码如下-

  factorialcalc<-函数(i){阶乘<-1if(i == 0 | i == 1){阶乘<-1} 别的{while(i> = 1){阶乘<-阶乘* i我<-i-1}}回报(因子)} 

带有输入-

  mynum<-5factorialcalc(mynum) 

并输出-

  [1] 120 

您可能想知道，您的代码可以完美运行，所以出了什么问题?"我的问题在于问题的一部分，即计算并存储".

如何修改我的代码以将factorialcalc的答案放入向量中?

示例-我输入

  mynum<-5factorialcalc(mynum) 

和

  mynum<-3factorialcalc(mynum) 

和

  mynum<-4factorialcalc(mynum) 

当我调用这个新矢量时，我想看到一个带有所有三个输出的矢量(所以几乎就像我制作了一个向量c(120,6,24))

我在想有一种方法可以将此向量添加到函数或while循环中的某个位置，但是我不确定在哪里.另外，请注意，答案必须包含一个循环，就像我的代码中一样.

解决方案

选项1.

矢量化"；您的功能

 #只需将整个内容包装在Vectorize()中Factorialcalc = Vectorize(function(i){阶乘<-1if(i == 0 | i == 1){阶乘<-1} 别的{while(i> = 1){阶乘<-阶乘* i我<-i-1}}回报(因子)})#现在，当您提供向量时，它会在每个元素上运行>Factorialcalc(c(5，3，4))[1] 120 6 24 

选项2.

使用旨在将单个功能应用于所提供矢量的多个元素的功能.使用 purrr 包中的 map_dbl ，您可以调用:

  map_dbl(c(5，3，4)，factorialcalc) 

哪个函数将 vector 中的每个元素提供给函数 factorialcalc ，并在返回矢量之前将每个结果连接起来.

使用 base R ，您可以简单地使用 apply -family函数:

  sapply(c(5，3，4)，factorialcalc) 

并获得相同的结果.

示例

 >map_dbl(c(5，3，4)，factorialcalc)[1] 120 6 24>sapply(c(5，3，4)，factorialcalc)[1] 120 6 24 

I was prompted a question and am ever so close to solving what I need. The question is as follows-

"Write a while loop that computes and stores as a new object, the factorial of any non-negative integer mynum by decrementing mynum by 1 at each repetition of the braced code."

Another factor was that if 0 or 1 was entered, the output would be 1.

The code that I wrote as follows-

factorialcalc <- function(i){
  factorial <- 1
  if(i==0 | i==1){
    factorial <- 1
  } else{
    while(i >= 1){
      factorial <- factorial * i
      i <- i-1
    }
  }
  return (factorial)
}

with inputs-

mynum <- 5
factorialcalc(mynum)

and output-

[1] 120

You may be wondering, "your code works perfect, so what's the issue?" My issue lies in the part of the question that says "computes AND stores."

How can I modify my code to put the answers of factorialcalc into a vector?

Example- I input

mynum <- 5
factorialcalc(mynum)

and

mynum <- 3
factorialcalc(mynum)

and

mynum <- 4
factorialcalc(mynum)

When I call this new vector, I would like to see a vector with all three of their outputs (so almost like I made a vector c(120,6,24))

I'm thinking there's a way to add this vector somewhere in my function or while loop, but I'm not sure where. Also, please note that the answer must contain a loop like in my code.

解决方案

Option 1.

"Vectorize" your function

# simply wrap the whole thing in Vectorize()
Factorialcalc = Vectorize(function(i){
  factorial <- 1
  if(i==0 | i==1){
    factorial <- 1
  } else{
    while(i >= 1){
      factorial <- factorial * i
      i <- i-1
    }
  }
  return (factorial)
})
# Now when you supply it a vector, it runs on each element
> Factorialcalc(c(5, 3, 4))
[1] 120   6  24

Option 2.

Use functions that are designed to apply a single function to multiple elements of a supplied vector. Using map_dbl from the purrr package, you can call:

map_dbl(c(5, 3, 4), factorialcalc)

Which supplies to your function factorialcalc each element in vector and concatenates each result before returning a vector.

Using base R you can simply use the apply-family functions:

sapply(c(5, 3, 4), factorialcalc)

and get the same result.

Example

> map_dbl(c(5, 3, 4), factorialcalc)
[1] 120   6  24
> sapply(c(5, 3, 4), factorialcalc)
[1] 120   6  24

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