R * not meaningful for factors ERROR

Question

I have the following data.frame and I want to perform some calculations on the 2nd column.

> test  
  code age
1  101  15
2  102  25
3  103  16
4  104          


        

Answer 1

new[,2] is a factor, not a numeric vector. Transform it first

new$MY_NEW_COLUMN <-as.numeric(as.character(new[,2])) * 5