com.thanglequoc.aqicalculator.NowCastCalculator Maven / Gradle / Ivy

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AQI Calculator give the detail result from AQI calculation. It also supports NowCast
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package com.thanglequoc.aqicalculator;

/**
 * A small size calculator use to calculate NowCast Concentration from an
 * array set of concentration. The NowCast concentration will be send back to
 * AQICalculator object to calculate the AQI, which will then represent
 * NowCast AQI
 *
 * @author ThangLeQuoc
 */
class NowCastCalculator {
    
    double getNowCastConcentration(Pollutant pollutant, double[] data) {
        if (!PollutantHelper.isPollutantValidForNowCastAQICalculation(pollutant) || !isValidNowCastData(data))
            return -1;
        return truncateConcentration(pollutant, data);
        
    }
    
    private double truncateConcentration(Pollutant pollutant, double[] data) {
        double weight = getWeightFactor(pollutant, data);
        double totalConcentrationWithWeight = 0;
        double totalWeight = 0;
        PollutantConcentrationTruncator truncator = new PollutantConcentrationTruncator();
        int indexDataSlot = getArraySizeToLoopForPollutant(pollutant);
        for (int i = 0; i < indexDataSlot; i++) {
            if (data[i] < 0)
                continue;
            else {
                totalConcentrationWithWeight += data[i] * Math.pow(weight, i);
                totalWeight += Math.pow(weight, i);
            }
        }
        return truncator.getTruncatedPollutantConcentrationBaseOnPollutant(pollutant,
                totalConcentrationWithWeight / totalWeight);
        
    }
    
    private int getArraySizeToLoopForPollutant(Pollutant pollutant) {
        if (Pollutant.PM10.equals(pollutant) || Pollutant.PM25.equals(pollutant)) {
            return 11;
        }
        return 7;
    }

    /**
     * A valid NowCast dataset must have at least two of the most recent 3 hours
     * */
    private boolean isValidNowCastData(double[] data) {
        int missingData = 0;
        for (int i = 0; i < 3; i++) {
            if (data[i] < 0) {
                missingData++;
            }
        }
        return (missingData >= 2) ? false : true;
    }
    
    private double getWeightFactor(Pollutant pollutant, double[] data) {
        double maxConcentration = Double.MIN_VALUE;
        double minConcentration = Double.MAX_VALUE;
        for (double i : data) {
            if (i < 0)
                continue;
            else {
                if (i > maxConcentration) {
                    maxConcentration = i;
                }
                if (i < minConcentration) {
                    minConcentration = i;
                }
            }
            
        }
        
        if (Pollutant.O3.equals(pollutant)) {
            /* No minimum weight factor for Ozone */
            double range = maxConcentration - minConcentration;
            double weightFactor = 1 - range / maxConcentration;
            return weightFactor;
        } else {
            /* For Particulate Matter, Minimum weight factor is 0.5 */
            double range = maxConcentration - minConcentration;
            double weightFactor = 1 - range / maxConcentration;
            return (weightFactor > 0.5) ? weightFactor : 0.5;
        }
    }
}