I have panel data in which my cross-sectional units are farms. I am correcting a variable for the years farmed by the operator. For some farms, it starts at 0, but these farms have data, so the value should be 1. I would need to add 1 for each year for the farms that start out at 0 years, but am unsure how to do that across farms. To be more clear, for the farms that start at 0, I need to add 1 to the years farmed variable for every year for that farm. - Thank you in advance.