matrixops.java

这是一个matlab的java实现。里面有许多内容。请大家慢慢捉摸。

/* Copyright (C) 2003 Univ. of Massachusetts Amherst, Computer Science Dept.
This file is part of "MALLET" (MAchine Learning for LanguagE Toolkit).
http://www.cs.umass.edu/~mccallum/mallet
This software is provided under the terms of the Common Public License,
version 1.0, as published by http://www.opensource.org.  For further
information, see the file `LICENSE' included with this distribution. */

package edu.umass.cs.mallet.base.types;

/** 
 *  A class of static utility functions for manipulating arrays of
 *   double. 
 */
public final class MatrixOps
{

	/** Sets every element of a double array to a given value.
	 * @param m  The array to modify
	 * @param v  The value
   * @deprecated Use java.util.Arrays.fill
	 */
    public static void setAll (double[] m, double v) {
        for (int i = 0; i < m.length; i++) m[i] = v;
    }

    public static void set (double[] dest, double[] source) {
			// XXX  Huh? This if-statement won't work. Java is pass-by-value, buddy. -cas
        if (source.length != dest.length)
            dest  = new double [source.length];
        System.arraycopy (source, 0, dest, 0, source.length);
    }

	/**
	 *  Multiplies every element in an array by a scalar.
	 *  @param m The array
	 *  @param factor The scalar
	 */
    public static void timesEquals (double[] m, double factor) {
        for (int i=0; i < m.length; i++)
            m[i] *= factor;
    }
    
    /* Calculates the Schur/Hadamard product */ // JJW
    public static void timesEquals(double[] m1, double[] m2) {

        assert (m1.length == m2.length) : "unequal lengths\n";
        for (int i=0; i < m1.length; i++) {
	    m1[i] *= m2[i];
	}
    }

	/**
	 *  Adds a scalar to every element in an array.
	 *  @param m The array
	 *  @param toadd The scalar
	 */
    public static void plusEquals (double[] m, double toadd) {
        for (int i=0; i < m.length; i++)
            m[i] += toadd;
    }

    public static void plusEquals (double[] m1, double[] m2) {
        assert (m1.length == m2.length) : "unequal lengths\n";
        for (int i=0; i < m1.length; i++) {
            if (Double.isInfinite(m1[i]) && Double.isInfinite(m2[i]) && (m1[i]*m2[i] < 0))
                m1[i] = 0.0;
            else
                m1[i] += m2[i];
        }
    }

    public static void plusEquals (double[] m1, double[] m2,  double factor) {
        assert (m1.length == m2.length) : "unequal lengths\n";
        for (int i=0; i < m1.length; i++) {
            double m1i = m1[i];
            double m2i = m2[i];
            if (Double.isInfinite(m1i) && Double.isInfinite(m2i) && (m1[i]*m2[i] < 0))
                m1[i] = 0.0;
            else  m1[i] += m2[i] * factor;
        }
    }



    /** Deprecated.  Use dotProduct() */
    public static double dot (double[] m1, double[] m2) {
        assert (m1.length == m2.length) : "m1.length != m2.length\n";
        double ret = 0.0;
        for (int i=0; i < m1.length; i++)
            ret += m1[i] * m2[i];
        return ret;
    }

    public static double dotProduct (double[] m1, double[] m2) {
        assert (m1.length == m2.length) : "m1.length != m2.length\n";
        double ret = 0.0;
        for (int i=0; i < m1.length; i++)
            ret += m1[i] * m2[i];
        return ret;
    }

    public static double absNorm (double[] m) {
        double ret = 0;
        for (int i = 0; i < m.length; i++)
            ret += Math.abs(m[i]);
        return ret;
    }

    public static double twoNorm (double[] m) {
        double ret = 0;
        for (int i = 0; i < m.length; i++)
            ret += m[i] * m[i];
        return Math.sqrt (ret);
    }


    public static double oneNorm (double[] m) {
        double ret = 0;
        for (int i = 0; i < m.length; i++)
            ret += m[i];
        return ret;
    }

    public static double infinityNorm (double[] m) {
        double ret = Double.NEGATIVE_INFINITY;
        for (int i = 0; i < m.length; i++)
            if (Math.abs(m[i]) > ret)
                ret = Math.abs(m[i]);
        return ret;
    }

    public static double absNormalize (double[] m) {
        double norm = absNorm(m);
        if (norm > 0)
            for (int i = 0; i < m.length; i++)
                m[i] /= norm;
        return norm;
    }

    public static double twoNormalize (double[] m) {
        double norm = twoNorm(m);
        if (norm > 0)
            for (int i = 0; i < m.length; i++)
                m[i] /= norm;
        return norm;
    }

    public static void substitute (double[] m, double oldValue, double newValue) {
        for (int i = m.length-1; i >= 0; i--)
            if (m[i] == oldValue)
                m[i] = newValue;
    }

    /** If "ifSelected" is false, it reverses the selection.  If
     "fselection" is null, this implies that all features are
     selected; all values in the row will be changed unless
     "ifSelected" is false. */
    public static final void rowSetAll (double[] m, int nc, int ri, double v, FeatureSelection fselection, boolean ifSelected) {
        if (fselection == null) {
            if (ifSelected == true) {
                for (int ci = 0; ci < nc; ci++)
                    m[ri*nc+ci] = v;
            }
        } else {
            // xxx Temporary check for full selection
            //assert (fselection.nextDeselectedIndex (0) == nc);
            for (int ci = 0; ci < nc; ci++)
                if (fselection.contains(ci) ^ !ifSelected)
                    m[ri*nc+ci] = v;
        }
    }

    public static double rowDotProduct (double[] m, int nc, int ri,
                                        Vector v, int maxCi,
                                        FeatureSelection selection) {
        return rowDotProduct (m, nc, ri, v, 1, maxCi, selection);
    }

    public static double rowDotProduct (double[] m, int nc, int ri,
                                        Vector v, double factor, int maxCi,
                                        FeatureSelection selection) {
        double ret = 0;
        if (selection != null) {
            for (int cil = 0; cil < v.numLocations(); cil++) {
                int ci = v.indexAtLocation (cil);
                if (selection.contains(ci) && ci < nc && ci <= maxCi)
                    ret += m[ri*nc+ci] * v.valueAtLocation(cil) * factor;
            }
        } else {
            for (int cil = 0; cil < v.numLocations(); cil++) {
                int ci = v.indexAtLocation (cil);
                if (ci < nc && ci <= maxCi)
                    ret += m[ri*nc+ci] * v.valueAtLocation(cil) * factor;
            }
        }
        return ret;
    }

    public static final void rowPlusEquals (double[] m, int nc, int ri,
                                            Vector v, double factor) {
        for (int vli = 0; vli < v.numLocations(); vli++)
            m[ri*nc+v.indexAtLocation(vli)] += v.valueAtLocation(vli) * factor;

    }

    public static boolean isNaN(double[] m) {
        for (int i = 0; i < m.length; i++)
            if (Double.isNaN(m[i]))
                return true;
        return false;
    }

    public static double sum (double[] m) {
        double sum = 0;
        for (int i = 0; i < m.length; i++)
            sum += m[i];
        return sum;
    }

    public static double sum (double[][] m) {
        double sum = 0;
        for (int i = 0; i < m.length; i++)
          for (int j = 0; j < m[i].length; j++)
            sum += m[i][j];
        return sum;
    }

    public static int sum (int[] m) {
        int sum = 0;
        for (int i = 0; i < m.length; i++)
            sum += m[i];
        return sum;
    }


    public static double mean (double[] m) {
        double sum = 0;
        for (int i = 0; i < m.length; i++)
            sum += m[i];
        return sum / m.length;
    }

    /** Return the standard deviation */
    public static double stddev (double[] m) {
        double mean = mean (m);
        double s = 0;
        for (int i = 0; i < m.length; i++)
            s += (m[i] - mean) * (m[i] - mean);
        return Math.sqrt (s/m.length);
        // Some prefer dividing by (m.length-1), but this is also common
    }

    public static double stderr (double[] m ) {
        return stddev(m) / Math.sqrt (m.length);
    }

    public static final void print (double[] m) {
        for (int i = 0; i < m.length; i++) {
            System.out.print (" " + m[i]);
        }
        System.out.println("");
    }

    public static final void print (double[][] arr)
    {
      for (int i = 0; i < arr.length; i++) {
        double[] doubles = arr[i];
        print (doubles);
      }
    }

    /** Print a space-separated array of elements
     * 
     * @param m An array of any type
     */
    public static final String toString( Object m ) {
	StringBuffer sb = new StringBuffer();
	
	int n=java.lang.reflect.Array.getLength(m)-1;
	for (int i = 0; i<n ; i++) {
	    sb.append(java.lang.reflect.Array.get(m,i));
	    sb.append(" ");
	}

	if (n>=0)
	    sb.append(java.lang.reflect.Array.get(m,n));

	return sb.toString();
    }

  public static final void printInRows (double[] arr)
  {
    for (int i = 0; i < arr.length; i++) {
      double v = arr[i];
      System.out.println("["+i+"]  "+arr[i]);
    }
  }

}