org.apache.commons.math3.linear.RRQRDecomposition Java Examples

/**
 * @param data dense matrix represented in row-major form
 * @return solver for the system Ax = b
 */
static Solver getSolver(double[][] data) {
  if (data == null) {
    return null;
  }
  RealMatrix M = new Array2DRowRealMatrix(data, false);
  double infNorm = M.getNorm();
  double singularityThreshold = infNorm * SINGULARITY_THRESHOLD_RATIO;
  RRQRDecomposition decomposition = new RRQRDecomposition(M, singularityThreshold);
  DecompositionSolver solver = decomposition.getSolver();
  if (solver.isNonSingular()) {
    return new Solver(solver);
  }
  // Otherwise try to report apparent rank
  int apparentRank = decomposition.getRank(0.01); // Better value?
  log.warn("{} x {} matrix is near-singular (threshold {}). Add more data or decrease the " +
           "number of features, to <= about {}",
           M.getRowDimension(), 
           M.getColumnDimension(),
           singularityThreshold,
           apparentRank);
  throw new SingularMatrixSolverException(apparentRank, "Apparent rank: " + apparentRank);
}
 

@Override
public Solver getSolver(RealMatrix M) {
  if (M == null) {
    return null;
  }
  RRQRDecomposition decomposition = new RRQRDecomposition(M, SINGULARITY_THRESHOLD);
  DecompositionSolver solver = decomposition.getSolver();
  if (solver.isNonSingular()) {
    return new CommonsMathSolver(solver);
  }
  // Otherwise try to report apparent rank
  int apparentRank = decomposition.getRank(0.01); // Better value?
  log.warn("{} x {} matrix is near-singular (threshold {}). Add more data or decrease the value of model.features, " +
           "to <= about {}",
           M.getRowDimension(), 
           M.getColumnDimension(), 
           SINGULARITY_THRESHOLD,
           apparentRank);
  throw new SingularMatrixSolverException(apparentRank, "Apparent rank: " + apparentRank);
}
 

/**
 * Calculates the parameters of a bivariate quadratic equation.
 * 
 * @param elevationValues the window of points to use.
 * @return the parameters of the bivariate quadratic equation as [a, b, c, d, e, f]
 */
private static double[] calculateParameters( final double[][] elevationValues ) {
    int rows = elevationValues.length;
    int cols = elevationValues[0].length;
    int pointsNum = rows * cols;

    final double[][] xyMatrix = new double[pointsNum][6];
    final double[] valueArray = new double[pointsNum];

    // TODO check on resolution
    int index = 0;
    for( int y = 0; y < rows; y++ ) {
        for( int x = 0; x < cols; x++ ) {
            xyMatrix[index][0] = x * x; // x^2
            xyMatrix[index][1] = y * y; // y^2
            xyMatrix[index][2] = x * y; // xy
            xyMatrix[index][3] = x; // x
            xyMatrix[index][4] = y; // y
            xyMatrix[index][5] = 1;
            valueArray[index] = elevationValues[y][x];
            index++;
        }
    }

    RealMatrix A = MatrixUtils.createRealMatrix(xyMatrix);
    RealVector z = MatrixUtils.createRealVector(valueArray);

    DecompositionSolver solver = new RRQRDecomposition(A).getSolver();
    RealVector solution = solver.solve(z);

    // start values for a, b, c, d, e, f, all set to 0.0
    final double[] parameters = solution.toArray();
    return parameters;
}
 

@Override
public boolean isNonSingular(RealMatrix M) {
  QRDecomposition decomposition = new RRQRDecomposition(M, SINGULARITY_THRESHOLD);
  DecompositionSolver solver = decomposition.getSolver();
  return solver.isNonSingular();
}