Question

I have a zoo class data set loaded into R and I am trying to run a for loop. But I keep running into the error

Error in NextMethod(“[<-“) : subscript out of bounds.

The loop is pretty simple

startobs=5
for (i in startobs:(NROW(data)-startobs)) {
  data[startobs+i,"dummy"]=startobs+i

}

I think the problem is in the startobs+i. R doesn’t seem to like placing the index of the loop (i) in the data[i,], as your going through each element. What am I doing wrong?

---

The structure of the data is as follows

>data

     obs     date   weight  dummy
      1   2010-10-04 52495   NA 
      2   2010-10-01 53000   NA 
      3   2010-09-30 52916   NA 
      4   2010-09-29 52785   NA 
      5   2010-09-28 53348   NA 
      6   2010-09-27 52885   NA 
      7   2010-09-24 52174   NA 
      8   2010-09-23 51461   NA 
      9   2010-09-22 51286   NA 
      10  2010-09-21 50968   NA 
      11  2010-09-20 49250   NA

and

>dput(head(data))
structure(c(100, 101.01, 110.75, 111.24, 104.96, 104.95, 104.06, 
109.08, 113.48, 111.6, 108, 107.95, 95.96, 100.5, 109.05, 103.57, 
103.88, 104.66, 100.34, 108.31, 109.4, 104.87, 106, 107.91, 22351900, 
11428600, 9137200, 7631300, 4598900, 3551000, 100.34, 108.31, 
109.4, 104.87, 106, 107.91, NA, NA, NA, NA, NA, NA), .Dim = 6:7, .Dimnames = list(
    NULL, c("weight", "height", "BMI", "Age", "Age2", "Intr", 
    "Chol")), index = structure(c(12649, 12650, 12653, 12654, 
12655, 12656), class = "Date"), class = "zoo")

Answer 1

You mean to do:

for (i in 1:NROW(data)) {
    data[i, "dummy"] = i
}

However, whatever you’re trying to do in a for loop will probably be easier with a vectorized solution, such as one using ifelse.