jQuery.each(data.root,function(key,value){
for(var i = 0 ; i < value.length; i++ ){
  var tmpArr = [];
  var obj = value[i];
  //tmpArr.push(obj["collectDate"]);
  tmpArr.push(3*i);
  tmpArr.push(obj["kpiValue"]);
  
  arr.push(tmpArr);
  myChart.setTooltip(tmpArr);
}