After you've imported the data to be analyzed in a data frame, you need to prepare it for further analysis. There are quite a few possible ways to retrieve values from a data frame. You can refer to the data by position, or by using the subscript notation. However, if you use a single subscript only, then you retrieve columns defined by the subscript and all rows. The same is true if you use a vector of column names only, without specifying the rows. If you specify two indexes or index ranges, then the first one is used for rows and the second one for columns. The following code shows these options:
TM[1:2]; # Two columns TM[c("MaritalStatus", "Gender")]; # Two columns TM[1:3,1:2]; # Three rows, two columns ...
