MathArrays.java
/*
* 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.math4.legacy.core;
import java.lang.reflect.Array;
import java.util.Arrays;
import java.util.Iterator;
import java.util.TreeSet;
import org.apache.commons.numbers.core.Precision;
import org.apache.commons.math4.legacy.exception.DimensionMismatchException;
import org.apache.commons.math4.legacy.exception.MathArithmeticException;
import org.apache.commons.math4.legacy.exception.MathIllegalArgumentException;
import org.apache.commons.math4.legacy.exception.MathInternalError;
import org.apache.commons.math4.legacy.exception.NoDataException;
import org.apache.commons.math4.legacy.exception.NonMonotonicSequenceException;
import org.apache.commons.math4.legacy.exception.NotANumberException;
import org.apache.commons.math4.legacy.exception.NotPositiveException;
import org.apache.commons.math4.legacy.exception.NotStrictlyPositiveException;
import org.apache.commons.math4.legacy.exception.NullArgumentException;
import org.apache.commons.math4.legacy.exception.NumberIsTooLargeException;
import org.apache.commons.math4.legacy.exception.NotFiniteNumberException;
import org.apache.commons.math4.legacy.exception.util.LocalizedFormats;
import org.apache.commons.math4.core.jdkmath.JdkMath;
/**
* Arrays utilities.
*
* @since 3.0
*/
public final class MathArrays {
/**
* Private constructor.
*/
private MathArrays() {}
/**
* Real-valued function that operate on an array or a part of it.
* @since 3.1
*/
public interface Function {
/**
* Operates on an entire array.
*
* @param array Array to operate on.
* @return the result of the operation.
*/
double evaluate(double[] array);
/**
* @param array Array to operate on.
* @param startIndex Index of the first element to take into account.
* @param numElements Number of elements to take into account.
* @return the result of the operation.
*/
double evaluate(double[] array,
int startIndex,
int numElements);
}
/**
* Create a copy of an array scaled by a value.
*
* @param arr Array to scale.
* @param val Scalar.
* @return scaled copy of array with each entry multiplied by val.
* @since 3.2
*/
public static double[] scale(double val, final double[] arr) {
double[] newArr = new double[arr.length];
for (int i = 0; i < arr.length; i++) {
newArr[i] = arr[i] * val;
}
return newArr;
}
/**
* <p>Multiply each element of an array by a value.</p>
*
* <p>The array is modified in place (no copy is created).</p>
*
* @param arr Array to scale
* @param val Scalar
* @since 3.2
*/
public static void scaleInPlace(double val, final double[] arr) {
for (int i = 0; i < arr.length; i++) {
arr[i] *= val;
}
}
/**
* Creates an array whose contents will be the element-by-element
* addition of the arguments.
*
* @param a First term of the addition.
* @param b Second term of the addition.
* @return a new array {@code r} where {@code r[i] = a[i] + b[i]}.
* @throws DimensionMismatchException if the array lengths differ.
* @since 3.1
*/
public static double[] ebeAdd(double[] a, double[] b) {
checkEqualLength(a, b);
final double[] result = a.clone();
for (int i = 0; i < a.length; i++) {
result[i] += b[i];
}
return result;
}
/**
* Creates an array whose contents will be the element-by-element
* subtraction of the second argument from the first.
*
* @param a First term.
* @param b Element to be subtracted.
* @return a new array {@code r} where {@code r[i] = a[i] - b[i]}.
* @throws DimensionMismatchException if the array lengths differ.
* @since 3.1
*/
public static double[] ebeSubtract(double[] a, double[] b) {
checkEqualLength(a, b);
final double[] result = a.clone();
for (int i = 0; i < a.length; i++) {
result[i] -= b[i];
}
return result;
}
/**
* Creates an array whose contents will be the element-by-element
* multiplication of the arguments.
*
* @param a First factor of the multiplication.
* @param b Second factor of the multiplication.
* @return a new array {@code r} where {@code r[i] = a[i] * b[i]}.
* @throws DimensionMismatchException if the array lengths differ.
* @since 3.1
*/
public static double[] ebeMultiply(double[] a, double[] b) {
checkEqualLength(a, b);
final double[] result = a.clone();
for (int i = 0; i < a.length; i++) {
result[i] *= b[i];
}
return result;
}
/**
* Creates an array whose contents will be the element-by-element
* division of the first argument by the second.
*
* @param a Numerator of the division.
* @param b Denominator of the division.
* @return a new array {@code r} where {@code r[i] = a[i] / b[i]}.
* @throws DimensionMismatchException if the array lengths differ.
* @since 3.1
*/
public static double[] ebeDivide(double[] a, double[] b) {
checkEqualLength(a, b);
final double[] result = a.clone();
for (int i = 0; i < a.length; i++) {
result[i] /= b[i];
}
return result;
}
/**
* Calculates the L<sub>1</sub> (sum of abs) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>1</sub> distance between the two points
* @throws DimensionMismatchException if the array lengths differ.
*/
public static double distance1(double[] p1, double[] p2) {
checkEqualLength(p1, p2);
double sum = 0;
for (int i = 0; i < p1.length; i++) {
sum += JdkMath.abs(p1[i] - p2[i]);
}
return sum;
}
/**
* Calculates the L<sub>1</sub> (sum of abs) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>1</sub> distance between the two points
* @throws DimensionMismatchException if the array lengths differ.
*/
public static int distance1(int[] p1, int[] p2) {
checkEqualLength(p1, p2);
int sum = 0;
for (int i = 0; i < p1.length; i++) {
sum += JdkMath.abs(p1[i] - p2[i]);
}
return sum;
}
/**
* Calculates the L<sub>2</sub> (Euclidean) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>2</sub> distance between the two points
* @throws DimensionMismatchException if the array lengths differ.
*/
public static double distance(double[] p1, double[] p2) {
checkEqualLength(p1, p2);
double sum = 0;
for (int i = 0; i < p1.length; i++) {
final double dp = p1[i] - p2[i];
sum += dp * dp;
}
return JdkMath.sqrt(sum);
}
/**
* Calculates the L<sub>2</sub> (Euclidean) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>2</sub> distance between the two points
* @throws DimensionMismatchException if the array lengths differ.
*/
public static double distance(int[] p1, int[] p2) {
checkEqualLength(p1, p2);
double sum = 0;
for (int i = 0; i < p1.length; i++) {
final double dp = (double) p1[i] - p2[i];
sum += dp * dp;
}
return JdkMath.sqrt(sum);
}
/**
* Calculates the L<sub>∞</sub> (max of abs) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>∞</sub> distance between the two points
* @throws DimensionMismatchException if the array lengths differ.
*/
public static double distanceInf(double[] p1, double[] p2) {
checkEqualLength(p1, p2);
double max = 0;
for (int i = 0; i < p1.length; i++) {
max = JdkMath.max(max, JdkMath.abs(p1[i] - p2[i]));
}
return max;
}
/**
* Calculates the L<sub>∞</sub> (max of abs) distance between two points.
*
* @param p1 the first point
* @param p2 the second point
* @return the L<sub>∞</sub> distance between the two points
* @throws DimensionMismatchException if the array lengths differ.
*/
public static int distanceInf(int[] p1, int[] p2) {
checkEqualLength(p1, p2);
int max = 0;
for (int i = 0; i < p1.length; i++) {
max = JdkMath.max(max, JdkMath.abs(p1[i] - p2[i]));
}
return max;
}
/**
* Specification of ordering direction.
*/
public enum OrderDirection {
/** Constant for increasing direction. */
INCREASING,
/** Constant for decreasing direction. */
DECREASING
}
/**
* Check that an array is monotonically increasing or decreasing.
*
* @param <T> the type of the elements in the specified array
* @param val Values.
* @param dir Ordering direction.
* @param strict Whether the order should be strict.
* @return {@code true} if sorted, {@code false} otherwise.
*/
public static <T extends Comparable<? super T>> boolean isMonotonic(T[] val,
OrderDirection dir,
boolean strict) {
T previous = val[0];
final int max = val.length;
for (int i = 1; i < max; i++) {
final int comp;
switch (dir) {
case INCREASING:
comp = previous.compareTo(val[i]);
if (strict) {
if (comp >= 0) {
return false;
}
} else {
if (comp > 0) {
return false;
}
}
break;
case DECREASING:
comp = val[i].compareTo(previous);
if (strict) {
if (comp >= 0) {
return false;
}
} else {
if (comp > 0) {
return false;
}
}
break;
default:
// Should never happen.
throw new MathInternalError();
}
previous = val[i];
}
return true;
}
/**
* Check that an array is monotonically increasing or decreasing.
*
* @param val Values.
* @param dir Ordering direction.
* @param strict Whether the order should be strict.
* @return {@code true} if sorted, {@code false} otherwise.
*/
public static boolean isMonotonic(double[] val, OrderDirection dir, boolean strict) {
return checkOrder(val, dir, strict, false);
}
/**
* Check that both arrays have the same length.
*
* @param a Array.
* @param b Array.
* @param abort Whether to throw an exception if the check fails.
* @return {@code true} if the arrays have the same length.
* @throws DimensionMismatchException if the lengths differ and
* {@code abort} is {@code true}.
* @since 3.6
*/
public static boolean checkEqualLength(double[] a,
double[] b,
boolean abort) {
if (a.length == b.length) {
return true;
} else {
if (abort) {
throw new DimensionMismatchException(a.length, b.length);
}
return false;
}
}
/**
* Check that both arrays have the same length.
*
* @param a Array.
* @param b Array.
* @throws DimensionMismatchException if the lengths differ.
* @since 3.6
*/
public static void checkEqualLength(double[] a,
double[] b) {
checkEqualLength(a, b, true);
}
/**
* Check that both arrays have the same length.
*
* @param a Array.
* @param b Array.
* @param abort Whether to throw an exception if the check fails.
* @return {@code true} if the arrays have the same length.
* @throws DimensionMismatchException if the lengths differ and
* {@code abort} is {@code true}.
* @since 3.6
*/
public static boolean checkEqualLength(int[] a,
int[] b,
boolean abort) {
if (a.length == b.length) {
return true;
} else {
if (abort) {
throw new DimensionMismatchException(a.length, b.length);
}
return false;
}
}
/**
* Check that both arrays have the same length.
*
* @param a Array.
* @param b Array.
* @throws DimensionMismatchException if the lengths differ.
* @since 3.6
*/
public static void checkEqualLength(int[] a,
int[] b) {
checkEqualLength(a, b, true);
}
/**
* Check that the given array is sorted.
*
* @param val Values.
* @param dir Ordering direction.
* @param strict Whether the order should be strict.
* @param abort Whether to throw an exception if the check fails.
* @return {@code true} if the array is sorted.
* @throws NonMonotonicSequenceException if the array is not sorted
* and {@code abort} is {@code true}.
*/
public static boolean checkOrder(double[] val, OrderDirection dir,
boolean strict, boolean abort) {
double previous = val[0];
final int max = val.length;
int index;
ITEM:
for (index = 1; index < max; index++) {
switch (dir) {
case INCREASING:
if (strict) {
if (val[index] <= previous) {
break ITEM;
}
} else {
if (val[index] < previous) {
break ITEM;
}
}
break;
case DECREASING:
if (strict) {
if (val[index] >= previous) {
break ITEM;
}
} else {
if (val[index] > previous) {
break ITEM;
}
}
break;
default:
// Should never happen.
throw new MathInternalError();
}
previous = val[index];
}
if (index == max) {
// Loop completed.
return true;
}
// Loop early exit means wrong ordering.
if (abort) {
throw new NonMonotonicSequenceException(val[index],
previous,
index,
dir == OrderDirection.INCREASING,
strict);
} else {
return false;
}
}
/**
* Check that the given array is sorted.
*
* @param val Values.
* @param dir Ordering direction.
* @param strict Whether the order should be strict.
* @throws NonMonotonicSequenceException if the array is not sorted.
* @since 2.2
*/
public static void checkOrder(double[] val, OrderDirection dir, boolean strict) {
checkOrder(val, dir, strict, true);
}
/**
* Check that the given array is sorted in strictly increasing order.
*
* @param val Values.
* @throws NonMonotonicSequenceException if the array is not sorted.
* @since 2.2
*/
public static void checkOrder(double[] val) {
checkOrder(val, OrderDirection.INCREASING, true);
}
/**
* Throws DimensionMismatchException if the input array is not rectangular.
*
* @param in array to be tested
* @throws NullArgumentException if input array is null
* @throws DimensionMismatchException if input array is not rectangular
* @since 3.1
*/
public static void checkRectangular(final long[][] in) {
NullArgumentException.check(in);
for (int i = 1; i < in.length; i++) {
if (in[i].length != in[0].length) {
throw new DimensionMismatchException(
LocalizedFormats.DIFFERENT_ROWS_LENGTHS,
in[i].length, in[0].length);
}
}
}
/**
* Check that all entries of the input array are strictly positive.
*
* @param in Array to be tested
* @throws NotStrictlyPositiveException if any entries of the array are not
* strictly positive.
* @since 3.1
*/
public static void checkPositive(final double[] in) {
for (double x : in) {
if (x <= 0) {
throw new NotStrictlyPositiveException(x);
}
}
}
/**
* Check that no entry of the input array is {@code NaN}.
*
* @param in Array to be tested.
* @throws NotANumberException if an entry is {@code NaN}.
* @since 3.4
*/
public static void checkNotNaN(final double[] in) {
for (double x : in) {
if (Double.isNaN(x)) {
throw new NotANumberException();
}
}
}
/**
* Check that all the elements are real numbers.
*
* @param val Arguments.
* @throws NotFiniteNumberException if any values of the array is not a
* finite real number.
*/
public static void checkFinite(final double[] val) {
for (double x : val) {
if (!Double.isFinite(x)) {
throw new NotFiniteNumberException(x);
}
}
}
/**
* Check that all entries of the input array are >= 0.
*
* @param in Array to be tested
* @throws NotPositiveException if any array entries are less than 0.
* @since 3.1
*/
public static void checkNonNegative(final long[] in) {
for (long i : in) {
if (i < 0) {
throw new NotPositiveException(i);
}
}
}
/**
* Check all entries of the input array are >= 0.
*
* @param in Array to be tested
* @throws NotPositiveException if any array entries are less than 0.
* @since 3.1
*/
public static void checkNonNegative(final long[][] in) {
for (int i = 0; i < in.length; i++) {
for (int j = 0; j < in[i].length; j++) {
if (in[i][j] < 0) {
throw new NotPositiveException(in[i][j]);
}
}
}
}
/**
* Returns true iff both arguments are null or have same dimensions and all
* their elements are equal as defined by
* {@link Precision#equals(float,float)}.
*
* @param x first array
* @param y second array
* @return true if the values are both null or have same dimension
* and equal elements.
*/
public static boolean equals(float[] x, float[] y) {
if (x == null || y == null) {
return (x == null) == (y == null);
}
if (x.length != y.length) {
return false;
}
for (int i = 0; i < x.length; ++i) {
if (!Precision.equals(x[i], y[i])) {
return false;
}
}
return true;
}
/**
* Returns true iff both arguments are null or have same dimensions and all
* their elements are equal as defined by
* {@link Precision#equalsIncludingNaN(double,double) this method}.
*
* @param x first array
* @param y second array
* @return true if the values are both null or have same dimension and
* equal elements
* @since 2.2
*/
public static boolean equalsIncludingNaN(float[] x, float[] y) {
if (x == null || y == null) {
return (x == null) == (y == null);
}
if (x.length != y.length) {
return false;
}
for (int i = 0; i < x.length; ++i) {
if (!Precision.equalsIncludingNaN(x[i], y[i])) {
return false;
}
}
return true;
}
/**
* Returns {@code true} iff both arguments are {@code null} or have same
* dimensions and all their elements are equal as defined by
* {@link Precision#equals(double,double)}.
*
* @param x First array.
* @param y Second array.
* @return {@code true} if the values are both {@code null} or have same
* dimension and equal elements.
*/
public static boolean equals(double[] x, double[] y) {
if (x == null || y == null) {
return (x == null) == (y == null);
}
if (x.length != y.length) {
return false;
}
for (int i = 0; i < x.length; ++i) {
if (!Precision.equals(x[i], y[i])) {
return false;
}
}
return true;
}
/**
* Returns {@code true} iff both arguments are {@code null} or have same
* dimensions and all their elements are equal as defined by
* {@link Precision#equalsIncludingNaN(double,double) this method}.
*
* @param x First array.
* @param y Second array.
* @return {@code true} if the values are both {@code null} or have same
* dimension and equal elements.
* @since 2.2
*/
public static boolean equalsIncludingNaN(double[] x, double[] y) {
if (x == null || y == null) {
return (x == null) == (y == null);
}
if (x.length != y.length) {
return false;
}
for (int i = 0; i < x.length; ++i) {
if (!Precision.equalsIncludingNaN(x[i], y[i])) {
return false;
}
}
return true;
}
/**
* Normalizes an array to make it sum to a specified value.
* Returns the result of the transformation
* <pre>
* x |-> x * normalizedSum / sum
* </pre>
* applied to each non-NaN element x of the input array, where sum is the
* sum of the non-NaN entries in the input array.
* <p>
* Throws IllegalArgumentException if {@code normalizedSum} is infinite
* or NaN and ArithmeticException if the input array contains any infinite elements
* or sums to 0.
* <p>
* Ignores (i.e., copies unchanged to the output array) NaNs in the input array.
*
* @param values Input array to be normalized
* @param normalizedSum Target sum for the normalized array
* @return the normalized array.
* @throws MathArithmeticException if the input array contains infinite
* elements or sums to zero.
* @throws MathIllegalArgumentException if the target sum is infinite or {@code NaN}.
* @since 2.1
*/
public static double[] normalizeArray(double[] values, double normalizedSum) {
if (Double.isInfinite(normalizedSum)) {
throw new MathIllegalArgumentException(LocalizedFormats.NORMALIZE_INFINITE);
}
if (Double.isNaN(normalizedSum)) {
throw new MathIllegalArgumentException(LocalizedFormats.NORMALIZE_NAN);
}
double sum = 0d;
final int len = values.length;
double[] out = new double[len];
for (int i = 0; i < len; i++) {
if (Double.isInfinite(values[i])) {
throw new MathIllegalArgumentException(LocalizedFormats.INFINITE_ARRAY_ELEMENT, values[i], i);
}
if (!Double.isNaN(values[i])) {
sum += values[i];
}
}
if (sum == 0) {
throw new MathArithmeticException(LocalizedFormats.ARRAY_SUMS_TO_ZERO);
}
final double scale = normalizedSum / sum;
for (int i = 0; i < len; i++) {
if (Double.isNaN(values[i])) {
out[i] = Double.NaN;
} else {
out[i] = values[i] * scale;
}
}
return out;
}
/** Build an array of elements.
* <p>
* Arrays are filled with field.getZero()
*
* @param <T> the type of the field elements
* @param field field to which array elements belong
* @param length of the array
* @return a new array
* @since 3.2
*/
public static <T> T[] buildArray(final Field<T> field, final int length) {
@SuppressWarnings("unchecked") // OK because field must be correct class
T[] array = (T[]) Array.newInstance(field.getRuntimeClass(), length);
Arrays.fill(array, field.getZero());
return array;
}
/** Build a double dimension array of elements.
* <p>
* Arrays are filled with field.getZero()
*
* @param <T> the type of the field elements
* @param field field to which array elements belong
* @param rows number of rows in the array
* @param columns number of columns (may be negative to build partial
* arrays in the same way <code>new Field[rows][]</code> works)
* @return a new array
* @since 3.2
*/
@SuppressWarnings("unchecked")
public static <T> T[][] buildArray(final Field<T> field, final int rows, final int columns) {
final T[][] array;
if (columns < 0) {
T[] dummyRow = buildArray(field, 0);
array = (T[][]) Array.newInstance(dummyRow.getClass(), rows);
} else {
array = (T[][]) Array.newInstance(field.getRuntimeClass(),
rows, columns);
for (int i = 0; i < rows; ++i) {
Arrays.fill(array[i], field.getZero());
}
}
return array;
}
/**
* Calculates the <a href="http://en.wikipedia.org/wiki/Convolution">
* convolution</a> between two sequences.
* <p>
* The solution is obtained via straightforward computation of the
* convolution sum (and not via FFT). Whenever the computation needs
* an element that would be located at an index outside the input arrays,
* the value is assumed to be zero.
*
* @param x First sequence.
* Typically, this sequence will represent an input signal to a system.
* @param h Second sequence.
* Typically, this sequence will represent the impulse response of the system.
* @return the convolution of {@code x} and {@code h}.
* This array's length will be {@code x.length + h.length - 1}.
* @throws NullArgumentException if either {@code x} or {@code h} is {@code null}.
* @throws NoDataException if either {@code x} or {@code h} is empty.
*
* @since 3.3
*/
public static double[] convolve(double[] x, double[] h) {
NullArgumentException.check(x);
NullArgumentException.check(h);
final int xLen = x.length;
final int hLen = h.length;
if (xLen == 0 || hLen == 0) {
throw new NoDataException();
}
// initialize the output array
final int totalLength = xLen + hLen - 1;
final double[] y = new double[totalLength];
// straightforward implementation of the convolution sum
for (int n = 0; n < totalLength; n++) {
double yn = 0;
int k = JdkMath.max(0, n + 1 - xLen);
int j = n - k;
while (k < hLen && j >= 0) {
yn += x[j--] * h[k++];
}
y[n] = yn;
}
return y;
}
/**
* Returns an array representing the natural number {@code n}.
*
* @param n Natural number.
* @return an array whose entries are the numbers 0, 1, ..., {@code n}-1.
* If {@code n == 0}, the returned array is empty.
*/
public static int[] natural(int n) {
return sequence(n, 0, 1);
}
/**
* Returns an array of {@code size} integers starting at {@code start},
* skipping {@code stride} numbers.
*
* @param size Natural number.
* @param start Natural number.
* @param stride Natural number.
* @return an array whose entries are the numbers
* {@code start, start + stride, ..., start + (size - 1) * stride}.
* If {@code size == 0}, the returned array is empty.
*
* @since 3.4
*/
public static int[] sequence(int size,
int start,
int stride) {
final int[] a = new int[size];
for (int i = 0; i < size; i++) {
a[i] = start + i * stride;
}
return a;
}
/**
* This method is used
* to verify that the input parameters designate a subarray of positive length.
* <ul>
* <li>returns <code>true</code> iff the parameters designate a subarray of
* positive length</li>
* <li>throws <code>MathIllegalArgumentException</code> if the array is null or
* or the indices are invalid</li>
* <li>returns <code>false</code> if the array is non-null, but
* <code>length</code> is 0.</li>
* </ul>
*
* @param values the input array
* @param begin index of the first array element to include
* @param length the number of elements to include
* @return true if the parameters are valid and designate a subarray of positive length
* @throws MathIllegalArgumentException if the indices are invalid or the array is null
* @since 3.3
*/
public static boolean verifyValues(final double[] values, final int begin, final int length) {
return verifyValues(values, begin, length, false);
}
/**
* This method is used
* to verify that the input parameters designate a subarray of positive length.
* <ul>
* <li>returns <code>true</code> iff the parameters designate a subarray of
* non-negative length</li>
* <li>throws <code>IllegalArgumentException</code> if the array is null or
* or the indices are invalid</li>
* <li>returns <code>false</code> if the array is non-null, but
* <code>length</code> is 0 unless <code>allowEmpty</code> is <code>true</code></li>
* </ul>
*
* @param values the input array
* @param begin index of the first array element to include
* @param length the number of elements to include
* @param allowEmpty if <code>true</code> then zero length arrays are allowed
* @return true if the parameters are valid
* @throws MathIllegalArgumentException if the indices are invalid or the array is null
* @since 3.3
*/
public static boolean verifyValues(final double[] values, final int begin,
final int length, final boolean allowEmpty) {
if (values == null) {
throw new NullArgumentException(LocalizedFormats.INPUT_ARRAY);
}
if (begin < 0) {
throw new NotPositiveException(LocalizedFormats.START_POSITION, Integer.valueOf(begin));
}
if (length < 0) {
throw new NotPositiveException(LocalizedFormats.LENGTH, Integer.valueOf(length));
}
if (begin + length > values.length) {
throw new NumberIsTooLargeException(LocalizedFormats.SUBARRAY_ENDS_AFTER_ARRAY_END,
Integer.valueOf(begin + length), Integer.valueOf(values.length), true);
}
return !(length == 0 && !allowEmpty);
}
/**
* This method is used
* to verify that the begin and length parameters designate a subarray of positive length
* and the weights are all non-negative, non-NaN, finite, and not all zero.
* <ul>
* <li>returns <code>true</code> iff the parameters designate a subarray of
* positive length and the weights array contains legitimate values.</li>
* <li>throws <code>IllegalArgumentException</code> if any of the following are true:
* <ul><li>the values array is null</li>
* <li>the weights array is null</li>
* <li>the weights array does not have the same length as the values array</li>
* <li>the weights array contains one or more infinite values</li>
* <li>the weights array contains one or more NaN values</li>
* <li>the weights array contains negative values</li>
* <li>the weights array does not contain at least one non-zero value (applies when length is non zero)</li>
* <li>the start and length arguments do not determine a valid array</li></ul>
* </li>
* <li>returns <code>false</code> if the array is non-null, but
* <code>length</code> is 0.</li>
* </ul>
*
* @param values the input array
* @param weights the weights array
* @param begin index of the first array element to include
* @param length the number of elements to include
* @return true if the parameters are valid and designate a subarray of positive length
* @throws MathIllegalArgumentException if the indices are invalid or the array is null
* @since 3.3
*/
public static boolean verifyValues(
final double[] values,
final double[] weights,
final int begin,
final int length) {
return verifyValues(values, weights, begin, length, false);
}
/**
* This method is used
* to verify that the begin and length parameters designate a subarray of positive length
* and the weights are all non-negative, non-NaN, finite, and not all zero.
* <ul>
* <li>returns <code>true</code> iff the parameters designate a subarray of
* non-negative length and the weights array contains legitimate values.</li>
* <li>throws <code>MathIllegalArgumentException</code> if any of the following are true:
* <ul><li>the values array is null</li>
* <li>the weights array is null</li>
* <li>the weights array does not have the same length as the values array</li>
* <li>the weights array contains one or more infinite values</li>
* <li>the weights array contains one or more NaN values</li>
* <li>the weights array contains negative values</li>
* <li>the weights array does not contain at least one non-zero value (applies when length is non zero)</li>
* <li>the start and length arguments do not determine a valid array</li></ul>
* </li>
* <li>returns <code>false</code> if the array is non-null, but
* <code>length</code> is 0 unless <code>allowEmpty</code> is <code>true</code>.</li>
* </ul>
*
* @param values the input array.
* @param weights the weights array.
* @param begin index of the first array element to include.
* @param length the number of elements to include.
* @param allowEmpty if {@code true} than allow zero length arrays to pass.
* @return {@code true} if the parameters are valid.
* @throws NullArgumentException if either of the arrays are null
* @throws MathIllegalArgumentException if the array indices are not valid,
* the weights array contains NaN, infinite or negative elements, or there
* are no positive weights.
* @since 3.3
*/
public static boolean verifyValues(final double[] values, final double[] weights,
final int begin, final int length, final boolean allowEmpty) {
if (weights == null || values == null) {
throw new NullArgumentException(LocalizedFormats.INPUT_ARRAY);
}
checkEqualLength(weights, values);
if (length != 0) {
boolean containsPositiveWeight = false;
for (int i = begin; i < begin + length; i++) {
final double weight = weights[i];
if (Double.isNaN(weight)) {
throw new MathIllegalArgumentException(LocalizedFormats.NAN_ELEMENT_AT_INDEX, Integer.valueOf(i));
}
if (Double.isInfinite(weight)) {
throw new MathIllegalArgumentException(LocalizedFormats.INFINITE_ARRAY_ELEMENT,
Double.valueOf(weight), Integer.valueOf(i));
}
if (weight < 0) {
throw new MathIllegalArgumentException(LocalizedFormats.NEGATIVE_ELEMENT_AT_INDEX,
Integer.valueOf(i), Double.valueOf(weight));
}
if (!containsPositiveWeight && weight > 0.0) {
containsPositiveWeight = true;
}
}
if (!containsPositiveWeight) {
throw new MathIllegalArgumentException(LocalizedFormats.WEIGHT_AT_LEAST_ONE_NON_ZERO);
}
}
return verifyValues(values, begin, length, allowEmpty);
}
/**
* Concatenates a sequence of arrays. The return array consists of the
* entries of the input arrays concatenated in the order they appear in
* the argument list. Null arrays cause NullPointerExceptions; zero
* length arrays are allowed (contributing nothing to the output array).
*
* @param x list of double[] arrays to concatenate
* @return a new array consisting of the entries of the argument arrays
* @throws NullPointerException if any of the arrays are null
* @since 3.6
*/
public static double[] concatenate(double[]... x) {
int combinedLength = 0;
for (double[] a : x) {
combinedLength += a.length;
}
int offset = 0;
int curLength = 0;
final double[] combined = new double[combinedLength];
for (int i = 0; i < x.length; i++) {
curLength = x[i].length;
System.arraycopy(x[i], 0, combined, offset, curLength);
offset += curLength;
}
return combined;
}
/**
* Returns an array consisting of the unique values in {@code data}.
* The return array is sorted in descending order. Empty arrays
* are allowed, but null arrays result in NullPointerException.
* Infinities are allowed. NaN values are allowed with maximum
* sort order - i.e., if there are NaN values in {@code data},
* {@code Double.NaN} will be the first element of the output array,
* even if the array also contains {@code Double.POSITIVE_INFINITY}.
*
* @param data array to scan
* @return descending list of values included in the input array
* @throws NullPointerException if data is null
* @since 3.6
*/
public static double[] unique(double[] data) {
TreeSet<Double> values = new TreeSet<>();
for (int i = 0; i < data.length; i++) {
values.add(data[i]);
}
final int count = values.size();
final double[] out = new double[count];
Iterator<Double> iterator = values.descendingIterator();
int i = 0;
while (iterator.hasNext()) {
out[i++] = iterator.next();
}
return out;
}
}