I know the question may seem stupid at first glance, but it's only because it's like R has a mind of its own, and doesn't let me in. :)
I did a questionnaire study, and one of the questions was 'For how many years have you been...?' I got 9 different numbers as answers, including both integers and decimals. I had designed the variable I named 'Years' to be a ratio or interval one. However, as I imported the data to R, it took it as a nominal variable with 9 levels. (By the way, the plan is to build a multiple linear regression model.)
How can I choose the type of variable I want to work with?