Group by SubTotal and Heading Print on Top of that Group

$(document).ready(function() {
    $('#example').DataTable( {
        order: [[2, 'asc']],        
        rowGroup: {
            startRender: null,
            endRender: function ( rows, group ) {
                var salaryAvg = rows
                    .data()
                    .pluck(5)
                    .reduce( function (a, b) {
                        return a + b.replace(/[^\d]/g, '')*1;
                    }, 0) / rows.count();
                salaryAvg = $.fn.dataTable.render.number(',', '.', 0, '$').display( salaryAvg );
 
                var ageAvg = rows
                    .data()
                    .pluck(3)
                    .reduce( function (a, b) {
                        return a + b*1;
                    }, 0) / rows.count();
 
                return $('<tr/>')
                    .append( '<td colspan="3">Averages for '+group+'</td>' )
                    .append( '<td>'+ageAvg.toFixed(0)+'</td>' )
                    .append( '<td/>' )
                    .append( '<td>'+salaryAvg+'</td>' );
            },
            dataSrc: 2
        }       
    } );
} );