function historyDataHandler(data) {
  // the last item in not a valid data point
  data.pop();
  //add data to the chart
  dataTable.addData(data);
}
/**
 * @param {Array} data raw data from server
 */
@param {Array} data raw data from server
@param { Array } data raw data from server
function historyDataHandler(data) {
  data.pop();
  dataTable.addData(data);
}
function historyDataHandler ( data ) { data . pop ( ) ; dataTable . addData ( data ) ; }
@param {Array} data raw data from server
@param { Array } data raw data from server
// the last item in not a valid data point //add data to the chart