You are using the template from this article yes? I wasn’t yet using an ARRAYFORMULA in this one. I see I based the tutorial on the new, updated version of this spreadsheet. Two options:
- You could make a copy of the updated sheet, and try the tutorial again: https://docs.google.com/spreadsheets/d/1KjK6ZChfEEP-XbWSniPtDPDN2YlOZUSni5d_Ij8t5FU/ (this one already has the array formula inside, you’d just need to add some empty rows as shown in the tutorial).
- Or: select the entire row I in the template from this article, and press backspace to delete it. If you then insert the ARRAYFORMULA (In I3 for January, I12 for February, I21 for March and so on) then it will work, and you won’t get the error.
The error “..because it would overwrite data” means that you should check what inside the cell the spreadsheet tells you. If you enter an array formula and give it a range of, for example, I3 to I6, that means it will need 4 empty rows below, including the cell where the formula starts.
Let me know if this helps!