jQuery and jqxGrid - how to select all rows in jqxGrid via checkboxes

jQuery and jqxGrid - how to select all rows in jqxGrid via checkboxes

How can I check all rows of jQWidgets jqxGrid with checkbox options
programmaticallyý? I can loop through rows and select them one-by-one or
use
$("#jqxgrid").jqxGrid('selectallrows');
but I need to make a selection via the checkbox option - see
http://www.jqwidgets.com/jquery-widgets-demo/demos/jqxgrid/index.htm?%28arctic%29#demos/jqxgrid/checkboxselection.htm
Basically I need to replicate a click on the top "Select All" checkbox.
How can I do this?
Thanks!