data.addColumn({type:'boolean',role:'certainty'}); // certainty col.

      data.addRows([
        [1,41.8,true],[2,32.4,//duplicate this
        [2,false],[3,25.7,[4,10.5,[5,10.4,[6,7.7,[7,9.6,[8,10.6,[9,14.8,[10,11.6,[11,4.7,[12,5.2,[13,3.6,[14,3.4,true]
      ]);