in R, the arguments of "for loop"

Question

Could anyone please tell me what is wrong with the R code below:

i = 1.001
#make SAV and STO become vector
SAV = c()
STO = c()
#set the initial values for the vector
SAV[1] = 0
STO[1] = 100


for (t in 2:1000) {
if ((price[t]>9.9)&（price[t]<10.1）&(SAV[t-1]!=0))
      SAV[t]=SAV[t-1]*i 
      STO[t]=0 
}

for (t in 2:1000) {
if ((price[t]>9.9)&（price[t]<10.1）&(SAV[t-1]=0))
      STO[t] = STO [t-1]
      SAV[t] = 0
}

SAV
STO

What I am trying to do is to find vector for both SAV and STO.

Answer 1

I'm not really good a R, but maybe the arrays start at 0? (instead at 1)

SAV[1] = 0
STO[1] = 100

==>

SAV[0] = 0
STO[0] = 100

And my second guess is regarding the if conditions in the for-loops. I would put brackets upon the whole expression, something like this.

for (t in 2:1000) {
  if ((price[t]>9.9)&（price[t]<10.1）&(SAV[t-1]=0)) {
      STO[t] = STO [t-1]
      SAV[t] = 0
  }
}

I hardly think it could help, but it's worth a try ;)

---

Edit:

Try to use SAV[t-1]==0 instead of SAV[t-1]=0 in your if condition ...

---

Edit 2:

Also try to use the && operator instead of the & one ...

Answer 2

I think you're overwriting the vectors STO and SAV each iteration. Hard to tell though because the price vector hasn't been declared. Try initializing STO and SAV as vectors of the desired length, rather than 0-length vectors:

SAV = matrix(0,1,1000)

STO = matrix(0,1,1000)

Answer 3

I would try something like the following. Modify it to be consistent with your program's logic

for (t in 2:1000) {
        if ((price[t]>9)&(price[t]<10)) {
             # values for STO,SAV when price in the interval and SAV[t-1]!=0
             if (SAV[t-1]!=0) { 
                SAV[t]=SAV[t-1]*i 
                STO[t]=0
             }
             # values for STO,SAV when price in the interval and SAV[t-1]==0
             else { 
               STO[t] = STO[t-1]
               SAV[t] = 0 
             }
        }
        # values for STO,SAV when price not in the interval
        else {   
           STO[t] = STO[t-1]
           SAV[t] = 1
        }
}