A for loop is probably not a good way to do what you want to do. Can you explain how you want to change the column TK110 and TK112? Can you post your data or a small part of it? The command
dput(head(sarjacikunitelistesi))
will give output that will allow other people to work with the first six rows of your data (if sarjacikunitelistesi is the name of your data frame). Please paste the output of that function between lines with three back ticks.
```
Your output
```