createHourlyValueMap = data => {
  if (!data || data.length === 0) {
    return {};
  }

  return data.reduce((acc, {hour, value}) => {
    if (acc[hour]) {
      acc[hour].push(value);
    } else {
      acc[hour] = [value];
    }
    return acc;
  }, {});
}
Derive an hashmap storing all the values for each hour as key
@param {array} data - input data of hour and value
@return an object with hour as key, and all values associate with that hour as value