columnvector.java

来自「一个一元曲线多项式数值演示例子」· Java 代码 · 共 156 行

package numbercruncher.matrix;

/**
 * A column vector.
 */
public class ColumnVector
    extends Matrix {
  //--------------//
  // Constructors //
  //--------------//

  /**
   * Constructor.
   * @param n the number of elements
   */
  public ColumnVector(int n) {
    super(n, 1);
  }

  /**
   * Constructor.
   * @param values the array of values
   */
  public ColumnVector(float values[]) {
    set(values);
  }

  /**
   * Constructor.
   * @param m the matrix (only the first column used)
   */
  private ColumnVector(Matrix m) {
    set(m);
  }

  //---------//
  // Getters //
  //---------//

  /**
   * Return this column vector's size.
   */
  public int size() {
    return nRows;
  }

  /**
   * Return the i'th value of the vector.
   * @param i the index
   * @return the value
   */
  public float at(int i) {
    return values[i][0];
  }

  /**
   * Copy the values of this matrix.
   * @return the copied values
   */
  public float[] copyValues1D() {
    float v[] = new float[nRows];

    for (int r = 0; r < nRows; ++r) {
      v[r] = values[r][0];
    }

    return v;
  }

  //---------//
  // Setters //
  //---------//

  /**
   * Set this column vector from a matrix.
   * Only the first column is used.
   * @param m the matrix
   */
  private void set(Matrix m) {
    this.nRows = m.nRows;
    this.nCols = 1;
    this.values = m.values;
  }

  /**
   * Set this column vector from an array of values.
   * @param values the array of values
   */
  protected void set(float values[]) {
    this.nRows = values.length;
    this.nCols = 1;
    this.values = new float[nRows][1];

    for (int r = 0; r < nRows; ++r) {
      this.values[r][0] = values[r];
    }
  }

  /**
   * Set the value of the i'th element.
   * @param i the index
   * @param value the value
   */
  public void set(int i, float value) {
    values[i][0] = value;
  }

  //-------------------//
  // Vector operations //
  //-------------------//

  /**
   * Add another column vector to this column vector.
   * @param cv the other column vector
   * @return the sum column vector
   * @throws numbercruncher.MatrixException for invalid size
   */
  public ColumnVector add(ColumnVector cv) throws MatrixException {
    return new ColumnVector(super.add(cv));
  }

  /**
   * Subtract another column vector from this column vector.
   * @param cv the other column vector
   * @return the sum column vector
   * @throws numbercruncher.MatrixException for invalid size
   */
  public ColumnVector subtract(ColumnVector cv) throws MatrixException {
    return new ColumnVector(super.subtract(cv));
  }

  /**
   * Compute the Euclidean norm.
   * @return the norm
   */
  public float norm() {
    double t = 0;

    for (int r = 0; r < nRows; ++r) {
      float v = values[r][0];
      t += v * v;
    }

    return (float) Math.sqrt(t);
  }

  /**
   * Print the vector values.
   */
  public void print() {
    for (int r = 0; r < nRows; ++r) {
      System.out.print("  " + values[r][0]);
    }
    System.out.println();
  }
}