Controls the layer groups in interactive maps (view mode): the layer control box (radio buttons or check boxes) and at which zoom levels the layers are displayed at.
tm_group(name, control = NA, zoom_levels = NA)group name that corresponds with the group name specified in the layer functions (e.g. tm_polygons())
The group control determines how
layer groups can be switched on and off. Options: "radio" for radio
buttons (meaning only one group can be shown), "check" for check boxes
(so multiple groups can be shown), and "none" for no control
(the group cannot be (de)selected).
The zoom levels at which the group is displays at. When specified control will be set to "none".