matrix: deleting moving clearing columns etc

I didn't see this in the manual and i can't find it in any contextual menus, so I'm beginning to think you can't, but....is there a way to do a drag all the clips in a column to another column? Or if I delete the contents of a column in Matrix,  why can't I move everything over to take up that now-blank space? Or can I clear a column without having to clear each individual cell?