for循环工作得很好，但是一旦我用它做一个函数，它突然就不会在R中给出正确的结果 [英] For loop works perfectly fine, but once I make a function out of it, it suddenly doesn't give the right results in R

问题描述

我有下面的for循环，正是我想要的:

I have the following for-loop which does exactly what I want:

for (t in 3:20){
    XX <- c(rep(0,22))

    for (k in (1:(t-2))){

        XX[k] <- (theta^(k-1) * (P[t-k] - P[t-k-1]))
                }
        X[t] = (1-theta)  * sum(XX) + theta^(t-1)
        P[t] <- D[t] + (0.7/0.3) * X[t] - 0.1*3^2*1*(20-t-1 + (1/0.3))  
            } 

但是，一旦我制作出一个函数并使用该函数，结果就会突然出错:

However, once I make a function out of and use the function the results are suddenly wrong:

BGJS <- function(theta){

for (t in 3:20){
    XX <- c(rep(0,22))

    for (k in (1:(t-2))){

        XX[k] <- (theta^(k-1) * (P[t-k] - P[t-k-1]))
                }
        X[t] = (1-theta)  * sum(XX) + theta^(t-1)
        P[t] <- D[t] + (0.7/0.3) * X[t] - 0.1*3^2*1*(20-t-1 + (1/0.3))  
            } 
    }

有人可以找到错误吗?

推荐答案

将<-和 = 更改为<<-因为您的范围在功能上有所不同.

Change <- and = to <<- as your scope is different in functions.

?<<-"

运算符<-和 = 分配到对其进行评估的环境中....

The operators <- and = assign into the environment in which they are evaluated. ...

运算符<-和->> 通常仅在函数中使用，并导致在父环境中搜索现有的分配变量的定义....

The operators <<- and ->> are normally only used in functions, and cause a search to be made through parent environments for an existing definition of the variable being assigned. ...

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