org.apache.mahout.math.DenseMatrix.java Source code

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Here is the source code for org.apache.mahout.math.DenseMatrix.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.mahout.math;

import org.apache.mahout.math.flavor.MatrixFlavor;

import java.util.Arrays;

/** Matrix of doubles implemented using a 2-d array */
public class DenseMatrix extends AbstractMatrix {

    private double[][] values;

    /**
     * Construct a matrix from the given values
     * 
     * @param values
     *          a double[][]
     */
    public DenseMatrix(double[][] values) {
        this(values, false);
    }

    /**
     * Construct a matrix from the given values
     *
     * @param values
     *          a double[][]
     * @param shallowCopy directly use the supplied array?
     */
    public DenseMatrix(double[][] values, boolean shallowCopy) {
        super(values.length, values[0].length);
        if (shallowCopy) {
            this.values = values;
        } else {
            this.values = new double[values.length][];
            for (int i = 0; i < values.length; i++) {
                this.values[i] = values[i].clone();
            }
        }
    }

    /**
     * Constructs an empty matrix of the given size.
     * @param rows  The number of rows in the result.
     * @param columns The number of columns in the result.
     */
    public DenseMatrix(int rows, int columns) {
        super(rows, columns);
        this.values = new double[rows][columns];
    }

    /**
     * Returns the backing array
     * @return double[][]
     */
    public double[][] getBackingStructure() {
        return this.values;
    }

    @Override
    public Matrix clone() {
        DenseMatrix clone = (DenseMatrix) super.clone();
        clone.values = new double[values.length][];
        for (int i = 0; i < values.length; i++) {
            clone.values[i] = values[i].clone();
        }
        return clone;
    }

    @Override
    public double getQuick(int row, int column) {
        return values[row][column];
    }

    @Override
    public Matrix like() {
        return like(rowSize(), columnSize());
    }

    @Override
    public Matrix like(int rows, int columns) {
        return new DenseMatrix(rows, columns);
    }

    @Override
    public void setQuick(int row, int column, double value) {
        values[row][column] = value;
    }

    @Override
    public Matrix viewPart(int[] offset, int[] size) {
        int rowOffset = offset[ROW];
        int rowsRequested = size[ROW];
        int columnOffset = offset[COL];
        int columnsRequested = size[COL];

        return viewPart(rowOffset, rowsRequested, columnOffset, columnsRequested);
    }

    @Override
    public Matrix viewPart(int rowOffset, int rowsRequested, int columnOffset, int columnsRequested) {
        if (rowOffset < 0) {
            throw new IndexException(rowOffset, rowSize());
        }
        if (rowOffset + rowsRequested > rowSize()) {
            throw new IndexException(rowOffset + rowsRequested, rowSize());
        }
        if (columnOffset < 0) {
            throw new IndexException(columnOffset, columnSize());
        }
        if (columnOffset + columnsRequested > columnSize()) {
            throw new IndexException(columnOffset + columnsRequested, columnSize());
        }
        return new MatrixView(this, new int[] { rowOffset, columnOffset },
                new int[] { rowsRequested, columnsRequested });
    }

    @Override
    public Matrix assign(double value) {
        for (int row = 0; row < rowSize(); row++) {
            Arrays.fill(values[row], value);
        }
        return this;
    }

    public Matrix assign(DenseMatrix matrix) {
        // make sure the data field has the correct length
        if (matrix.values[0].length != this.values[0].length || matrix.values.length != this.values.length) {
            this.values = new double[matrix.values.length][matrix.values[0].length];
        }
        // now copy the values
        for (int i = 0; i < this.values.length; i++) {
            System.arraycopy(matrix.values[i], 0, this.values[i], 0, this.values[0].length);
        }
        return this;
    }

    @Override
    public Matrix assignColumn(int column, Vector other) {
        if (rowSize() != other.size()) {
            throw new CardinalityException(rowSize(), other.size());
        }
        if (column < 0 || column >= columnSize()) {
            throw new IndexException(column, columnSize());
        }
        for (int row = 0; row < rowSize(); row++) {
            values[row][column] = other.getQuick(row);
        }
        return this;
    }

    @Override
    public Matrix assignRow(int row, Vector other) {
        if (columnSize() != other.size()) {
            throw new CardinalityException(columnSize(), other.size());
        }
        if (row < 0 || row >= rowSize()) {
            throw new IndexException(row, rowSize());
        }
        for (int col = 0; col < columnSize(); col++) {
            values[row][col] = other.getQuick(col);
        }
        return this;
    }

    @Override
    public Vector viewRow(int row) {
        if (row < 0 || row >= rowSize()) {
            throw new IndexException(row, rowSize());
        }
        return new DenseVector(values[row], true);
    }

    @Override
    public MatrixFlavor getFlavor() {
        return MatrixFlavor.DENSELIKE;
    }
}