extracting subset

["Keun-Hyung Choi" <khchoi@sfsu.edu>]

Hello,

 

Suppose I have a data frame of 20 X 10, in which the columns can be regrouped differently by different categories. Let’s say I have three categories, which were stored as lists.

Then how  can I extract a column subset of A in category 1 & B in category 2, or a subset of B in category 2 & C in category 3, or a subset of  A in category 1 & B in category 2 & C in category 3?

 

Thanks. Keun-Hyung