These functions modify the selection or return the currently selected
(highlighted) cases.
iset.selected
returns a vector of IDs of all currently
selected cases (in the current iSet)
iset.select
changes the selection of the current
iSet. All plots are updated immediately to reflect the new selection.
iset.sel.changed
returns TRUE
if the selection
has changed since last call to this function.
iset.selectAll
selects everything
iset.selectNone
clears all selections (yes, not a good name)