net.intelie.liverig.plugin.widgets.Derivatives Maven / Gradle / Ivy

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package net.intelie.liverig.plugin.widgets;

import java.util.ArrayList;
import java.util.List;

public class Derivatives {
    private Double firstAverage;
    private List firstPoints;

    private Double secondAverage;
    private List secondPoints;

    public Double getFirstAverage() {
        return firstAverage;
    }

    public void setFirstAverage(Double firstAverage) {
        this.firstAverage = firstAverage;
    }

    public List getFirstPoints() {
        return firstPoints;
    }

    public void setFirstPoints(List firstPoints) {
        this.firstPoints = firstPoints;
    }

    public Double getSecondAverage() {
        return secondAverage;
    }

    public void setSecondAverage(Double secondAverage) {
        this.secondAverage = secondAverage;
    }

    public List getSecondPoints() {
        return secondPoints;
    }

    public void setSecondPoints(List secondPoints) {
        this.secondPoints = secondPoints;
    }

    /**
     * @param p1     First point
     * @param p2     Second point
     * @param factor Time unit: time is given in mls multiplying it by 1000 we can get it in s
     * @return The slope of the line between points p1 and p2
     */
    private Double slopeOfSegment(CurvePoint p1, CurvePoint p2, Double factor) {
        return ((p2.getY() - p1.getY()) / (p2.getX() - p1.getX())) * factor;
    }

    /**
     * The average rate of change of a function y = f(x)
     * from x = a to x = b is given by:
     * ( f(b) - f(a) ) / (b - a)
     * 
     * Here we use a = first and b = last
     *
     * @param y Curve original points
     * @return The average of the points of y'
     */
    private Double averageFirstDerivative(List y, Double factor) {
        return slopeOfSegment(y.get(0), y.get(y.size() - 1), factor);
    }

    /**
     * Computes an approximated first derivative by calculating
     * the slope of each segment of y
     *
     * @param y Original curve points
     * @return Approximated points of y'
     */
    private List firstDerivative(List y, Double factor) {
        List dydx = new ArrayList<>();

        for (int i = 0; i < y.size() - 1; i++) {
            Double slp = slopeOfSegment(y.get(i), y.get(i + 1), factor);

            dydx.add(new CurvePoint(y.get(i).getTimestamp(), y.get(i).getX(), slp));
        }

        return dydx;
    }

    /**
     * @param y2 Approximated second derivative points
     * @return Average of the points of y2
     */
    private Double averageSecondDerivative(List y2, Double factor) {
        return slopeOfSegment(y2.get(0), y2.get(y2.size() - 1), factor);
    }

    /**
     * Computes an approximated second derivative by calculating
     * the slope of each segment of y'
     *
     * @param y1 First derivative points
     * @return Approximated points of y''
     */
    private List secondDerivative(List y1, Double factor) {
        List dydx = new ArrayList<>();

        for (int i = 0; i < y1.size() - 1; i++) {
            Double slp = slopeOfSegment(y1.get(i), y1.get(i + 1), factor);

            dydx.add(new CurvePoint(y1.get(i).getTimestamp(), y1.get(i).getX(), slp));
        }

        return dydx;
    }

    public void calculate(List originalPoints, Double factor) {
        if (originalPoints.size() > 1) {
            firstAverage = averageFirstDerivative(originalPoints, factor);
            firstPoints = firstDerivative(originalPoints, factor);
        }

        if (firstPoints != null && firstPoints.size() > 1) {
            secondPoints = secondDerivative(firstPoints, factor);
            if (secondPoints.size() > 1) {
                secondAverage = averageSecondDerivative(secondPoints, factor);
            }
        }
    }

}