9.5 Column Vector

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	Java Number Cruncher: The Java Programmer's Guide to Numerical Computing By Ronald  Mak
	Table of Contents
	Chapter  9.   Basic Matrix Operations

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9.5 Column Vector

The ColumnVector class is another subclass of Matrix , and it is nearly identical to the RowVector class. See Listing 9-0f. One difference is that, whereas in class RowVector the set(float values[]) method could have the matrix reference the values argument directly, the same method in class ColumnVector must copy the argument vector to the first (and only) element of the matrix rows.

Listing 9-0f The ColumnVector class.

 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();     } } 

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