Java tutorial
/* * 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.commons.math3.linear; import java.io.Serializable; import org.apache.commons.math3.exception.DimensionMismatchException; import org.apache.commons.math3.exception.MathIllegalStateException; import org.apache.commons.math3.exception.NoDataException; import org.apache.commons.math3.exception.NotStrictlyPositiveException; import org.apache.commons.math3.exception.NullArgumentException; import org.apache.commons.math3.exception.NumberIsTooSmallException; import org.apache.commons.math3.exception.OutOfRangeException; import org.apache.commons.math3.exception.util.LocalizedFormats; import org.apache.commons.math3.util.MathUtils; /** * Implementation of {@link RealMatrix} using a {@code double[][]} array to * store entries. * * @version $Id: Array2DRowRealMatrix.java 1416643 2012-12-03 19:37:14Z tn $ */ public class Array2DRowRealMatrix extends AbstractRealMatrix implements Serializable { /** Serializable version identifier. */ private static final long serialVersionUID = -1067294169172445528L; /** Entries of the matrix. */ private double data[][]; /** * Creates a matrix with no data */ public Array2DRowRealMatrix() { } /** * Create a new RealMatrix with the supplied row and column dimensions. * * @param rowDimension Number of rows in the new matrix. * @param columnDimension Number of columns in the new matrix. * @throws NotStrictlyPositiveException if the row or column dimension is * not positive. */ public Array2DRowRealMatrix(final int rowDimension, final int columnDimension) throws NotStrictlyPositiveException { super(rowDimension, columnDimension); data = new double[rowDimension][columnDimension]; } /** * Create a new {@code RealMatrix} using the input array as the underlying * data array. * <p>The input array is copied, not referenced. This constructor has * the same effect as calling {@link #Array2DRowRealMatrix(double[][], boolean)} * with the second argument set to {@code true}.</p> * * @param d Data for the new matrix. * @throws DimensionMismatchException if {@code d} is not rectangular. * @throws NoDataException if {@code d} row or colum dimension is zero. * @throws NullArgumentException if {@code d} is {@code null}. * @see #Array2DRowRealMatrix(double[][], boolean) */ public Array2DRowRealMatrix(final double[][] d) throws DimensionMismatchException, NoDataException, NullArgumentException { copyIn(d); } /** * Create a new RealMatrix using the input array as the underlying * data array. * If an array is built specially in order to be embedded in a * RealMatrix and not used directly, the {@code copyArray} may be * set to {@code false}. This will prevent the copying and improve * performance as no new array will be built and no data will be copied. * * @param d Data for new matrix. * @param copyArray if {@code true}, the input array will be copied, * otherwise it will be referenced. * @throws DimensionMismatchException if {@code d} is not rectangular. * @throws NoDataException if {@code d} row or colum dimension is zero. * @throws NullArgumentException if {@code d} is {@code null}. * @see #Array2DRowRealMatrix(double[][]) */ public Array2DRowRealMatrix(final double[][] d, final boolean copyArray) throws DimensionMismatchException, NoDataException, NullArgumentException { if (copyArray) { copyIn(d); } else { if (d == null) { throw new NullArgumentException(); } final int nRows = d.length; if (nRows == 0) { throw new NoDataException(LocalizedFormats.AT_LEAST_ONE_ROW); } final int nCols = d[0].length; if (nCols == 0) { throw new NoDataException(LocalizedFormats.AT_LEAST_ONE_COLUMN); } for (int r = 1; r < nRows; r++) { if (d[r].length != nCols) { throw new DimensionMismatchException(d[r].length, nCols); } } data = d; } } /** * Create a new (column) RealMatrix using {@code v} as the * data for the unique column of the created matrix. * The input array is copied. * * @param v Column vector holding data for new matrix. */ public Array2DRowRealMatrix(final double[] v) { final int nRows = v.length; data = new double[nRows][1]; for (int row = 0; row < nRows; row++) { data[row][0] = v[row]; } } /** {@inheritDoc} */ @Override public RealMatrix createMatrix(final int rowDimension, final int columnDimension) throws NotStrictlyPositiveException { return new Array2DRowRealMatrix(rowDimension, columnDimension); } /** {@inheritDoc} */ @Override public RealMatrix copy() { return new Array2DRowRealMatrix(copyOut(), false); } /** * Compute the sum of {@code this} and {@code m}. * * @param m Matrix to be added. * @return {@code this + m}. * @throws MatrixDimensionMismatchException if {@code m} is not the same * size as {@code this}. */ public Array2DRowRealMatrix add(final Array2DRowRealMatrix m) throws MatrixDimensionMismatchException { // Safety check. MatrixUtils.checkAdditionCompatible(this, m); final int rowCount = getRowDimension(); final int columnCount = getColumnDimension(); final double[][] outData = new double[rowCount][columnCount]; for (int row = 0; row < rowCount; row++) { final double[] dataRow = data[row]; final double[] mRow = m.data[row]; final double[] outDataRow = outData[row]; for (int col = 0; col < columnCount; col++) { outDataRow[col] = dataRow[col] + mRow[col]; } } return new Array2DRowRealMatrix(outData, false); } /** * Returns {@code this} minus {@code m}. * * @param m Matrix to be subtracted. * @return {@code this - m} * @throws MatrixDimensionMismatchException if {@code m} is not the same * size as {@code this}. */ public Array2DRowRealMatrix subtract(final Array2DRowRealMatrix m) throws MatrixDimensionMismatchException { MatrixUtils.checkSubtractionCompatible(this, m); final int rowCount = getRowDimension(); final int columnCount = getColumnDimension(); final double[][] outData = new double[rowCount][columnCount]; for (int row = 0; row < rowCount; row++) { final double[] dataRow = data[row]; final double[] mRow = m.data[row]; final double[] outDataRow = outData[row]; for (int col = 0; col < columnCount; col++) { outDataRow[col] = dataRow[col] - mRow[col]; } } return new Array2DRowRealMatrix(outData, false); } /** * Returns the result of postmultiplying {@code this} by {@code m}. * * @param m matrix to postmultiply by * @return {@code this * m} * @throws DimensionMismatchException if * {@code columnDimension(this) != rowDimension(m)} */ public Array2DRowRealMatrix multiply(final Array2DRowRealMatrix m) throws DimensionMismatchException { MatrixUtils.checkMultiplicationCompatible(this, m); final int nRows = this.getRowDimension(); final int nCols = m.getColumnDimension(); final int nSum = this.getColumnDimension(); final double[][] outData = new double[nRows][nCols]; // Will hold a column of "m". final double[] mCol = new double[nSum]; final double[][] mData = m.data; // Multiply. for (int col = 0; col < nCols; col++) { // Copy all elements of column "col" of "m" so that // will be in contiguous memory. for (int mRow = 0; mRow < nSum; mRow++) { mCol[mRow] = mData[mRow][col]; } for (int row = 0; row < nRows; row++) { final double[] dataRow = data[row]; double sum = 0; for (int i = 0; i < nSum; i++) { sum += dataRow[i] * mCol[i]; } outData[row][col] = sum; } } return new Array2DRowRealMatrix(outData, false); } /** {@inheritDoc} */ @Override public double[][] getData() { return copyOut(); } /** * Get a reference to the underlying data array. * * @return 2-dimensional array of entries. */ public double[][] getDataRef() { return data; } /** {@inheritDoc} */ @Override public void setSubMatrix(final double[][] subMatrix, final int row, final int column) throws NoDataException, OutOfRangeException, DimensionMismatchException, NullArgumentException { if (data == null) { if (row > 0) { throw new MathIllegalStateException(LocalizedFormats.FIRST_ROWS_NOT_INITIALIZED_YET, row); } if (column > 0) { throw new MathIllegalStateException(LocalizedFormats.FIRST_COLUMNS_NOT_INITIALIZED_YET, column); } MathUtils.checkNotNull(subMatrix); final int nRows = subMatrix.length; if (nRows == 0) { throw new NoDataException(LocalizedFormats.AT_LEAST_ONE_ROW); } final int nCols = subMatrix[0].length; if (nCols == 0) { throw new NoDataException(LocalizedFormats.AT_LEAST_ONE_COLUMN); } data = new double[subMatrix.length][nCols]; for (int i = 0; i < data.length; ++i) { if (subMatrix[i].length != nCols) { throw new DimensionMismatchException(subMatrix[i].length, nCols); } System.arraycopy(subMatrix[i], 0, data[i + row], column, nCols); } } else { super.setSubMatrix(subMatrix, row, column); } } /** {@inheritDoc} */ @Override public double getEntry(final int row, final int column) throws OutOfRangeException { MatrixUtils.checkMatrixIndex(this, row, column); return data[row][column]; } /** {@inheritDoc} */ @Override public void setEntry(final int row, final int column, final double value) throws OutOfRangeException { MatrixUtils.checkMatrixIndex(this, row, column); data[row][column] = value; } /** {@inheritDoc} */ @Override public void addToEntry(final int row, final int column, final double increment) throws OutOfRangeException { MatrixUtils.checkMatrixIndex(this, row, column); data[row][column] += increment; } /** {@inheritDoc} */ @Override public void multiplyEntry(final int row, final int column, final double factor) throws OutOfRangeException { MatrixUtils.checkMatrixIndex(this, row, column); data[row][column] *= factor; } /** {@inheritDoc} */ @Override public int getRowDimension() { return (data == null) ? 0 : data.length; } /** {@inheritDoc} */ @Override public int getColumnDimension() { return ((data == null) || (data[0] == null)) ? 0 : data[0].length; } /** {@inheritDoc} */ @Override public double[] operate(final double[] v) throws DimensionMismatchException { final int nRows = this.getRowDimension(); final int nCols = this.getColumnDimension(); if (v.length != nCols) { throw new DimensionMismatchException(v.length, nCols); } final double[] out = new double[nRows]; for (int row = 0; row < nRows; row++) { final double[] dataRow = data[row]; double sum = 0; for (int i = 0; i < nCols; i++) { sum += dataRow[i] * v[i]; } out[row] = sum; } return out; } /** {@inheritDoc} */ @Override public double[] preMultiply(final double[] v) throws DimensionMismatchException { final int nRows = getRowDimension(); final int nCols = getColumnDimension(); if (v.length != nRows) { throw new DimensionMismatchException(v.length, nRows); } final double[] out = new double[nCols]; for (int col = 0; col < nCols; ++col) { double sum = 0; for (int i = 0; i < nRows; ++i) { sum += data[i][col] * v[i]; } out[col] = sum; } return out; } /** {@inheritDoc} */ @Override public double walkInRowOrder(final RealMatrixChangingVisitor visitor) { final int rows = getRowDimension(); final int columns = getColumnDimension(); visitor.start(rows, columns, 0, rows - 1, 0, columns - 1); for (int i = 0; i < rows; ++i) { final double[] rowI = data[i]; for (int j = 0; j < columns; ++j) { rowI[j] = visitor.visit(i, j, rowI[j]); } } return visitor.end(); } /** {@inheritDoc} */ @Override public double walkInRowOrder(final RealMatrixPreservingVisitor visitor) { final int rows = getRowDimension(); final int columns = getColumnDimension(); visitor.start(rows, columns, 0, rows - 1, 0, columns - 1); for (int i = 0; i < rows; ++i) { final double[] rowI = data[i]; for (int j = 0; j < columns; ++j) { visitor.visit(i, j, rowI[j]); } } return visitor.end(); } /** {@inheritDoc} */ @Override public double walkInRowOrder(final RealMatrixChangingVisitor visitor, final int startRow, final int endRow, final int startColumn, final int endColumn) throws OutOfRangeException, NumberIsTooSmallException { MatrixUtils.checkSubMatrixIndex(this, startRow, endRow, startColumn, endColumn); visitor.start(getRowDimension(), getColumnDimension(), startRow, endRow, startColumn, endColumn); for (int i = startRow; i <= endRow; ++i) { final double[] rowI = data[i]; for (int j = startColumn; j <= endColumn; ++j) { rowI[j] = visitor.visit(i, j, rowI[j]); } } return visitor.end(); } /** {@inheritDoc} */ @Override public double walkInRowOrder(final RealMatrixPreservingVisitor visitor, final int startRow, final int endRow, final int startColumn, final int endColumn) throws OutOfRangeException, NumberIsTooSmallException { MatrixUtils.checkSubMatrixIndex(this, startRow, endRow, startColumn, endColumn); visitor.start(getRowDimension(), getColumnDimension(), startRow, endRow, startColumn, endColumn); for (int i = startRow; i <= endRow; ++i) { final double[] rowI = data[i]; for (int j = startColumn; j <= endColumn; ++j) { visitor.visit(i, j, rowI[j]); } } return visitor.end(); } /** {@inheritDoc} */ @Override public double walkInColumnOrder(final RealMatrixChangingVisitor visitor) { final int rows = getRowDimension(); final int columns = getColumnDimension(); visitor.start(rows, columns, 0, rows - 1, 0, columns - 1); for (int j = 0; j < columns; ++j) { for (int i = 0; i < rows; ++i) { final double[] rowI = data[i]; rowI[j] = visitor.visit(i, j, rowI[j]); } } return visitor.end(); } /** {@inheritDoc} */ @Override public double walkInColumnOrder(final RealMatrixPreservingVisitor visitor) { final int rows = getRowDimension(); final int columns = getColumnDimension(); visitor.start(rows, columns, 0, rows - 1, 0, columns - 1); for (int j = 0; j < columns; ++j) { for (int i = 0; i < rows; ++i) { visitor.visit(i, j, data[i][j]); } } return visitor.end(); } /** {@inheritDoc} */ @Override public double walkInColumnOrder(final RealMatrixChangingVisitor visitor, final int startRow, final int endRow, final int startColumn, final int endColumn) throws OutOfRangeException, NumberIsTooSmallException { MatrixUtils.checkSubMatrixIndex(this, startRow, endRow, startColumn, endColumn); visitor.start(getRowDimension(), getColumnDimension(), startRow, endRow, startColumn, endColumn); for (int j = startColumn; j <= endColumn; ++j) { for (int i = startRow; i <= endRow; ++i) { final double[] rowI = data[i]; rowI[j] = visitor.visit(i, j, rowI[j]); } } return visitor.end(); } /** {@inheritDoc} */ @Override public double walkInColumnOrder(final RealMatrixPreservingVisitor visitor, final int startRow, final int endRow, final int startColumn, final int endColumn) throws OutOfRangeException, NumberIsTooSmallException { MatrixUtils.checkSubMatrixIndex(this, startRow, endRow, startColumn, endColumn); visitor.start(getRowDimension(), getColumnDimension(), startRow, endRow, startColumn, endColumn); for (int j = startColumn; j <= endColumn; ++j) { for (int i = startRow; i <= endRow; ++i) { visitor.visit(i, j, data[i][j]); } } return visitor.end(); } /** * Get a fresh copy of the underlying data array. * * @return a copy of the underlying data array. */ private double[][] copyOut() { final int nRows = this.getRowDimension(); final double[][] out = new double[nRows][this.getColumnDimension()]; // can't copy 2-d array in one shot, otherwise get row references for (int i = 0; i < nRows; i++) { System.arraycopy(data[i], 0, out[i], 0, data[i].length); } return out; } /** * Replace data with a fresh copy of the input array. * * @param in Data to copy. * @throws NoDataException if the input array is empty. * @throws DimensionMismatchException if the input array is not rectangular. * @throws NullArgumentException if the input array is {@code null}. */ private void copyIn(final double[][] in) throws DimensionMismatchException, NoDataException, NullArgumentException { setSubMatrix(in, 0, 0); } }