June 2017
Beginner to intermediate
576 pages
15h 22m
English
Running the colnames() function is a convenient way of obtaining the index numbers for each of the variables. Using index numbers in R functions is a convenient and fast way of referencing variables.
However, changes in file format can change the order, so using this method is only recommended for interactive use:

To simplify the example, we will eliminate variables 12, 13, 16, 19, 20, and 21 from the analysis