collapseGroup

Method which collapses a group. It receives as a parameterthe closest data row to the group header or directly the group header. The method accepts an optional parameter called Options.It provides more control over the collapse behavior.

"Options" parameter properties
expandChildren	Will expand all child groups
expandParents	Will expand all parent groups
collapseChildren	Will collapse all child groups
collapseParents	Will collapse all parent groups
toggleChildren	Will expand/collapse all child groups according to the state of the current group
toggleParents	Will expand/collapse all parent groups according to the state of the current group
findClosestGroup	Will expand the first parent group

Example:

function CollapseGroupUsingDataItem() {
    var masterTableView = $find("<%=RadGrid1.ClientID %>").get_masterTableView();
    masterTableView.collapseGroup(masterTableView.get_dataItems()[4].get_element(),
    {
        expandParents: true,
        expandChildren: false
    });
}

function CollapseGroupUsingGroupHeader() {
    var masterTableView = $find("<%=RadGrid1.ClientID %>").get_masterTableView();
    var groupHeader = $telerik.getElementsByClassName(masterTableView.get_element(), "rgGroupHeader")[4];
    masterTableView.collapseGroup(groupHeader,
    {
        expandChildren: false,
        findClosestGroup: true
    });
}