在R中使用if else语句进行for循环

Question

I know lots of people have posted about this, and I did look through the answers to write my code, but it's still not working... Can someone point out where i'm doing wrong please? many thanks in advance!

for(j in 1:1000){

        for(i in 1:52){

                   if (i == 1){
                        r.sims[i,] <- r.sims[1]
                        }
                 else if (i == 2){
                       r.sims[i,] <- r.sims[2]
                       }
                 else (i > 2){
                               r.sims[i,] <- r.sims[i-1,]*ar1 + r.sims[i-2,]*ar2 + e.sims[i,] + e.sims[i-1,]*ma1
                           }

                       }

                }

i have the following errors

Error: unexpected '{' in:
"       }
             else (i > 2){"
>                                r.sims[i,] <- r.sims[i-1,]*ar1 + r.sims[i-2,]*ar2 + e.sims[i,] + e.sims[i-1,]*ma1
Error in r.sims[i, ] <- r.sims[i - 1, ] * ar1 + r.sims[i - 2, ] * ar2 +  : 
  replacement has length zero
>                    }
Error: unexpected '}' in "                   }"
>                    
>                        }
Error: unexpected '}' in "                       }"
> 
>                 }
Error: unexpected '}' in "                }"
> 

Answer 1

You seem to misunderstand the concept of else .

else covers all cases that didn't match previous if or else if statements. Therefore, you cannot specify any condition for else .

To cover all cases where i is not 1 or 2 simply use else , without any () brackets.

If you want to have a condition, use else if (condition) .

Answer 2

Without understanding what your code is supposed to do, I have nevertheless made an example of how you might fix your script. I think the key is that you need to supply curly brackets {...} following your else statement in order for it to consider the following code.

Example:

r.sims <- matrix(runif(52)*100, nrow=52, ncol=100)
e.sims <- matrix(runif(52)*100, nrow=52, ncol=100)

ma1 <- 1
ar1 <- 2
ar2 <- 3

for(j in 1:1000) {
    for(i in 1:52) {
        if (i == 1) {
            r.sims[i,] <- r.sims[1]
        } else {
            if(i == 2) {
                r.sims[i,] <- r.sims[2]
            } else {
                if(i > 2) {
                    r.sims[i,] <- r.sims[i-1,]*ar1 + r.sims[i-2,]*ar2 + e.sims[i,] + e.sims[i-1,]*ma1
                }
            }
        }
    }
}