Quick Question
If you want to add new observations to a data frame, what should you use?
Explanation
To add new observations to a data frame with the same variable values, you should use rbind.
If you want to combine two vectors into a data frame, what should you use?
Explanation
To combine two vectors into a data frame, you should use data.frame.
If you want to add a variable to your data frame, what should you use?
Explanation
To add a variable to your data frame, you should the dollar sign notation.