I am trying to remove some rows in a for loop in R. The conditional involves comparing it to the line below it, so I can't filter within the brackets.

I know that I can remove a row when a constant is specified: `dataframe[-2, ]`. I just want to do the same with a variable: `dataframe[-x, ]`. Here's the full loop:

```
for (j in 1:(nrow(referrals) - 1)) {
  k <- j + 1
  if (referrals[j, "Client ID"] == referrals[k, "Client ID"] & 
      referrals[j, "Provider SubCode"] == referrals[k, "Provider SubCode"]) {
    referrals[-k, ]
  }
}

```

The code runs without complaint, but no rows are removed (and I know some should be). Of course, if it I test it with a constant, it works fine: `referrals[-2, ]`.