How to add a factor column to dataframe based on a conditional statement from another column?

Question

I have a dataframe for which I need to add a factor column based on a conditional statement. Here is the data.

Code:

    morstats.agri.f <- morocc         


        

Answer 1

you can use ifelse like this

dataframe$periodframe <- ifelse(dataframe$year > 1991,"post-1991", "pre-1991")