Example usage for org.apache.commons.math.linear RealMatrixImpl getDataRef

Introduction

In this page you can find the example usage for org.apache.commons.math.linear RealMatrixImpl getDataRef.

Prototype

public double[][] getDataRef() 

Source Link

Document

Returns a reference to the underlying data array.

Usage

From source file:com.lzy.heartset.sg.SGFilter.java

/**
 * Computes Savitzky-Golay coefficients for given parameters
 * /*from  w w w .  j a  v a  2  s.co  m*/
 * @param nl
 *            numer of past data points filter will use
 * @param nr
 *            number of future data points filter will use
 * @param degree
 *            order of smoothin polynomial
 * @return Savitzky-Golay coefficients
 * @throws IllegalArgumentException
 *             if {@code nl < 0} or {@code nr < 0} or {@code nl + nr <
 *             degree}
 */
public static double[] computeSGCoefficients(int nl, int nr, int degree) {
    if (nl < 0 || nr < 0 || nl + nr < degree)
        throw new IllegalArgumentException("Bad arguments");
    RealMatrixImpl matrix = new RealMatrixImpl(degree + 1, degree + 1);
    double[][] a = matrix.getDataRef();
    double sum;
    for (int i = 0; i <= degree; i++) {
        for (int j = 0; j <= degree; j++) {
            sum = (i == 0 && j == 0) ? 1 : 0;
            for (int k = 1; k <= nr; k++)
                sum += pow(k, i + j);
            for (int k = 1; k <= nl; k++)
                sum += pow(-k, i + j);
            a[i][j] = sum;
        }
    }
    double[] b = new double[degree + 1];
    b[0] = 1;
    b = matrix.solve(b);
    double[] coeffs = new double[nl + nr + 1];
    for (int n = -nl; n <= nr; n++) {
        sum = b[0];
        for (int m = 1; m <= degree; m++)
            sum += b[m] * pow(n, m);
        coeffs[n + nl] = sum;
    }
    return coeffs;
}

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