I am working with a dataset that has a "9" put, when the proband did not give an answer on what gender he/she is. I want to have these 9's exclueded from my data. The problem is that i do not want the other 9's in all the different colums to be excluded.
All the other missing values of the other variables are marked with "66", "77", "88", "99", and "999". I marked them as "NA" right when importing the data. But I don't know how to do it with the "9", since I dont want to have all the other 9's in the other colums (e.g jbstfy, happy) to be removed.
I hope you can help me out.
PS: Do i mark gender as a factor? or as character?