Why no delete column method?

[mdmcconnell]

Hi - I am investigating the use of datatable in my small project, and have a number of questions about the implementation. I do not see any way to delete a column from a table. Does this exist, or why not? Also, from the examples, it looks as though it is possible to apply an expr to a new column, but not to update a column in place, using an expr. Is that correct, or is there a way to apply expr to an existing column?