org.meteoinfo.math.interpolate.InterpUtil.java Source code

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Here is the source code for org.meteoinfo.math.interpolate.InterpUtil.java

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package org.meteoinfo.math.interpolate;

import org.apache.commons.math3.analysis.BivariateFunction;
import org.apache.commons.math3.analysis.UnivariateFunction;
import org.apache.commons.math3.analysis.interpolation.AkimaSplineInterpolator;
import org.apache.commons.math3.analysis.interpolation.BicubicInterpolator;
import org.apache.commons.math3.analysis.interpolation.BivariateGridInterpolator;
import org.apache.commons.math3.analysis.interpolation.DividedDifferenceInterpolator;
import org.apache.commons.math3.analysis.interpolation.LinearInterpolator;
import org.apache.commons.math3.analysis.interpolation.LoessInterpolator;
import org.apache.commons.math3.analysis.interpolation.NevilleInterpolator;
import org.apache.commons.math3.analysis.interpolation.SplineInterpolator;
import org.apache.commons.math3.analysis.interpolation.UnivariateInterpolator;
import org.apache.commons.math3.analysis.polynomials.PolynomialSplineFunction;
import org.meteoinfo.data.ArrayUtil;
import ucar.ma2.Array;
import ucar.ma2.DataType;

/**
 *
 * @author Yaqiang Wang
 */
public class InterpUtil {

    /**
     * Make linear interpolation function - PolynomialSplineFunction
     * @param x X data
     * @param y Y data
     * @return Linear interpolation function
     */
    public static PolynomialSplineFunction linearInterpFunc(Array x, Array y) {
        double[] xd = (double[]) ArrayUtil.copyToNDJavaArray(x);
        double[] yd = (double[]) ArrayUtil.copyToNDJavaArray(y);
        LinearInterpolator li = new LinearInterpolator();
        PolynomialSplineFunction psf = li.interpolate(xd, yd);

        return psf;
    }

    /**
     * Make interpolation function
     * @param x X data
     * @param y Y data
     * @param kind Specifies the kind of interpolation as a string (linear, 'spline').
     * @return Interpolation function
     */
    public static UnivariateFunction getInterpFunc(Array x, Array y, String kind) {
        double[] xd = (double[]) ArrayUtil.copyToNDJavaArray(x);
        double[] yd = (double[]) ArrayUtil.copyToNDJavaArray(y);
        UnivariateInterpolator li;
        switch (kind) {
        case "spline":
        case "cubic":
            li = new SplineInterpolator();
            break;
        case "akima":
            li = new AkimaSplineInterpolator();
            break;
        case "divided":
            li = new DividedDifferenceInterpolator();
            break;
        case "loess":
            li = new LoessInterpolator();
            break;
        case "neville":
            li = new NevilleInterpolator();
            break;
        default:
            li = new LinearInterpolator();
            break;
        }
        UnivariateFunction psf = li.interpolate(xd, yd);

        return psf;
    }

    /**
     * Make interpolation function for grid data
     * @param x X data
     * @param y Y data
     * @param z Z data
     * @return Interpolation function
     */
    public static BivariateFunction getBiInterpFunc(Array x, Array y, Array z) {
        double[] xd = (double[]) ArrayUtil.copyToNDJavaArray(x);
        double[] yd = (double[]) ArrayUtil.copyToNDJavaArray(y);
        double[][] zd = (double[][]) ArrayUtil.copyToNDJavaArray(z);
        BivariateGridInterpolator li = new BicubicInterpolator();
        BivariateFunction func = li.interpolate(xd, yd, zd);

        return func;
    }

    /**
     * Compute the value of the function
     * @param func The function
     * @param x Input data
     * @return Function value
     */
    public static Array evaluate(UnivariateFunction func, Array x) {
        Array r = Array.factory(DataType.DOUBLE, x.getShape());
        for (int i = 0; i < r.getSize(); i++)
            r.setDouble(i, func.value(x.getDouble(i)));

        return r;
    }

    /**
     * Compute the value of the function
     * @param func The function
     * @param x Input data
     * @return Function value
     */
    public static double evaluate(UnivariateFunction func, Number x) {
        return func.value(x.doubleValue());
    }

    /**
     * Compute the value of the function
     * @param func The function
     * @param x Input x data
     * @param y Input y data
     * @return Function value
     */
    public static Array evaluate(BivariateFunction func, Array x, Array y) {
        Array r = Array.factory(DataType.DOUBLE, x.getShape());
        for (int i = 0; i < r.getSize(); i++)
            r.setDouble(i, func.value(x.getDouble(i), y.getDouble(i)));

        return r;
    }

    /**
     * Compute the value of the function
     * @param func The function
     * @param x Input x data
     * @param y Input y data
     * @return Function value
     */
    public static double evaluate(BivariateFunction func, Number x, Number y) {
        return func.value(x.doubleValue(), y.doubleValue());
    }
}