rent: aqiFromPm(pm2_5),
          trend: Math.abs(trend) > 5 ? trend : 0,
          details: json
        };
      }

      function aqiFromPm(pm) {
        const table = [
          [0.0, 12.0, 0, 50],
          [12.1, 35.4, 51, 100],
          [35.5, 55.4, 101, 150],
          [55.5, 150.4, 151, 200],
          [150.5, 250.4, 201, 300],
          [250.5, 500.4, 301, 500],
        ];
        const computeAqi = (concI, [concLo, concHi, aqiLo, aqiHi]) =>
          Math.round(
            ((concI - concLo) / 