MathArrays (Apache Commons Math 3.6.1 API)

java.lang.Object
- org.apache.commons.math3.util.MathArrays

```
public class MathArrays
extends Object
```
Arrays utilities.

Since:

3.0

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static interface`	`MathArrays.Function` Real-valued function that operate on an array or a part of it.
`static class`	`MathArrays.OrderDirection` Specification of ordering direction.
`static class`	`MathArrays.Position` Specification for indicating that some operation applies before or after a given index.

Method Summary

Methods
Modifier and Type	Method and Description
`static <T> T[]`	`buildArray(Field<T> field, int length)` Build an array of elements.
`static <T> T[][]`	`buildArray(Field<T> field, int rows, int columns)` Build a double dimension array of elements.
`static void`	`checkEqualLength(double[] a, double[] b)` Check that both arrays have the same length.
`static boolean`	`checkEqualLength(double[] a, double[] b, boolean abort)` Check that both arrays have the same length.
`static void`	`checkEqualLength(int[] a, int[] b)` Check that both arrays have the same length.
`static boolean`	`checkEqualLength(int[] a, int[] b, boolean abort)` Check that both arrays have the same length.
`static void`	`checkNonNegative(long[] in)` Check that all entries of the input array are >= 0.
`static void`	`checkNonNegative(long[][] in)` Check all entries of the input array are >= 0.
`static void`	`checkNotNaN(double[] in)` Check that no entry of the input array is `NaN`.
`static void`	`checkOrder(double[] val)` Check that the given array is sorted in strictly increasing order.
`static void`	`checkOrder(double[] val, MathArrays.OrderDirection dir, boolean strict)` Check that the given array is sorted.
`static boolean`	`checkOrder(double[] val, MathArrays.OrderDirection dir, boolean strict, boolean abort)` Check that the given array is sorted.
`static void`	`checkPositive(double[] in)` Check that all entries of the input array are strictly positive.
`static void`	`checkRectangular(long[][] in)` Throws DimensionMismatchException if the input array is not rectangular.
`static double[]`	`concatenate(double[]... x)` Concatenates a sequence of arrays.
`static double[]`	`convolve(double[] x, double[] h)` Calculates the convolution between two sequences.
`static double[]`	`copyOf(double[] source)` Creates a copy of the `source` array.
`static double[]`	`copyOf(double[] source, int len)` Creates a copy of the `source` array.
`static int[]`	`copyOf(int[] source)` Creates a copy of the `source` array.
`static int[]`	`copyOf(int[] source, int len)` Creates a copy of the `source` array.
`static double[]`	`copyOfRange(double[] source, int from, int to)` Creates a copy of the `source` array.
`static double`	`cosAngle(double[] v1, double[] v2)` Calculates the cosine of the angle between two vectors.
`static double`	`distance(double[] p1, double[] p2)` Calculates the L₂ (Euclidean) distance between two points.
`static double`	`distance(int[] p1, int[] p2)` Calculates the L₂ (Euclidean) distance between two points.
`static double`	`distance1(double[] p1, double[] p2)` Calculates the L₁ (sum of abs) distance between two points.
`static int`	`distance1(int[] p1, int[] p2)` Calculates the L₁ (sum of abs) distance between two points.
`static double`	`distanceInf(double[] p1, double[] p2)` Calculates the L_∞ (max of abs) distance between two points.
`static int`	`distanceInf(int[] p1, int[] p2)` Calculates the L_∞ (max of abs) distance between two points.
`static double[]`	`ebeAdd(double[] a, double[] b)` Creates an array whose contents will be the element-by-element addition of the arguments.
`static double[]`	`ebeDivide(double[] a, double[] b)` Creates an array whose contents will be the element-by-element division of the first argument by the second.
`static double[]`	`ebeMultiply(double[] a, double[] b)` Creates an array whose contents will be the element-by-element multiplication of the arguments.
`static double[]`	`ebeSubtract(double[] a, double[] b)` Creates an array whose contents will be the element-by-element subtraction of the second argument from the first.
`static boolean`	`equals(double[] x, double[] y)` Returns `true` iff both arguments are `null` or have same dimensions and all their elements are equal as defined by `Precision.equals(double,double)`.
`static boolean`	`equals(float[] x, float[] y)` Returns true iff both arguments are null or have same dimensions and all their elements are equal as defined by `Precision.equals(float,float)`.
`static boolean`	`equalsIncludingNaN(double[] x, double[] y)` Returns `true` iff both arguments are `null` or have same dimensions and all their elements are equal as defined by `this method`.
`static boolean`	`equalsIncludingNaN(float[] x, float[] y)` Returns true iff both arguments are null or have same dimensions and all their elements are equal as defined by `this method`.
`static boolean`	`isMonotonic(double[] val, MathArrays.OrderDirection dir, boolean strict)` Check that an array is monotonically increasing or decreasing.
`static <T extends Comparable<? super T>> boolean`	`isMonotonic(T[] val, MathArrays.OrderDirection dir, boolean strict)` Check that an array is monotonically increasing or decreasing.
`static double`	`linearCombination(double[] a, double[] b)` Compute a linear combination accurately.
`static double`	`linearCombination(double a1, double b1, double a2, double b2)` Compute a linear combination accurately.
`static double`	`linearCombination(double a1, double b1, double a2, double b2, double a3, double b3)` Compute a linear combination accurately.
`static double`	`linearCombination(double a1, double b1, double a2, double b2, double a3, double b3, double a4, double b4)` Compute a linear combination accurately.
`static int[]`	`natural(int n)` Returns an array representing the natural number `n`.
`static double[]`	`normalizeArray(double[] values, double normalizedSum)` Normalizes an array to make it sum to a specified value.
`static double`	`safeNorm(double[] v)` Returns the Cartesian norm (2-norm), handling both overflow and underflow.
`static double[]`	`scale(double val, double[] arr)` Create a copy of an array scaled by a value.
`static void`	`scaleInPlace(double val, double[] arr)` Multiply each element of an array by a value.
`static int[]`	`sequence(int size, int start, int stride)` Returns an array of `size` integers starting at `start`, skipping `stride` numbers.
`static void`	`shuffle(int[] list)` Shuffle the entries of the given array.
`static void`	`shuffle(int[] list, int start, MathArrays.Position pos)` Shuffle the entries of the given array.
`static void`	`shuffle(int[] list, int start, MathArrays.Position pos, RandomGenerator rng)` Shuffle the entries of the given array, using the Fisher–Yates algorithm.
`static void`	`shuffle(int[] list, RandomGenerator rng)` Shuffle the entries of the given array.
`static void`	`sortInPlace(double[] x, double[]... yList)` Sort an array in ascending order in place and perform the same reordering of entries on other arrays.
`static void`	`sortInPlace(double[] x, MathArrays.OrderDirection dir, double[]... yList)` Sort an array in place and perform the same reordering of entries on other arrays.
`static double[]`	`unique(double[] data)` Returns an array consisting of the unique values in `data`.
`static boolean`	`verifyValues(double[] values, double[] weights, int begin, int length)` 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.
`static boolean`	`verifyValues(double[] values, double[] weights, int begin, int length, boolean 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.
`static boolean`	`verifyValues(double[] values, int begin, int length)` This method is used to verify that the input parameters designate a subarray of positive length.
`static boolean`	`verifyValues(double[] values, int begin, int length, boolean allowEmpty)` This method is used to verify that the input parameters designate a subarray of positive length.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

scale
```
public static double[] scale(double val,
             double[] arr)
```
Create a copy of an array scaled by a value.

Parameters:
arr - Array to scale.
val - Scalar.

Returns:
scaled copy of array with each entry multiplied by val.
Since:

3.2

scaleInPlace
```
public static void scaleInPlace(double val,
                double[] arr)
```
Multiply each element of an array by a value.

The array is modified in place (no copy is created).

Parameters:
arr - Array to scale
val - Scalar
Since:

3.2

ebeAdd
```
public static double[] ebeAdd(double[] a,
              double[] b)
                       throws DimensionMismatchException
```
Creates an array whose contents will be the element-by-element addition of the arguments.

Parameters:
a - First term of the addition.
b - Second term of the addition.

Returns:
a new array r where r[i] = a[i] + b[i].

Throws:

DimensionMismatchException - if the array lengths differ.
Since:

3.1

ebeSubtract
```
public static double[] ebeSubtract(double[] a,
                   double[] b)
                            throws DimensionMismatchException
```
Creates an array whose contents will be the element-by-element subtraction of the second argument from the first.

Parameters:
a - First term.
b - Element to be subtracted.

Returns:
a new array r where r[i] = a[i] - b[i].

Throws:

DimensionMismatchException - if the array lengths differ.
Since:

3.1

ebeMultiply
```
public static double[] ebeMultiply(double[] a,
                   double[] b)
                            throws DimensionMismatchException
```
Creates an array whose contents will be the element-by-element multiplication of the arguments.

Parameters:
a - First factor of the multiplication.
b - Second factor of the multiplication.

Returns:
a new array r where r[i] = a[i] * b[i].

Throws:

DimensionMismatchException - if the array lengths differ.
Since:

3.1

ebeDivide
```
public static double[] ebeDivide(double[] a,
                 double[] b)
                          throws DimensionMismatchException
```
Creates an array whose contents will be the element-by-element division of the first argument by the second.

Parameters:
a - Numerator of the division.
b - Denominator of the division.

Returns:
a new array r where r[i] = a[i] / b[i].

Throws:

DimensionMismatchException - if the array lengths differ.
Since:

3.1

distance1
```
public static double distance1(double[] p1,
               double[] p2)
                        throws DimensionMismatchException
```
Calculates the L₁ (sum of abs) distance between two points.

Parameters:
p1 - the first point
p2 - the second point

Returns:
the L₁ distance between the two points

Throws:

DimensionMismatchException - if the array lengths differ.

distance1
```
public static int distance1(int[] p1,
            int[] p2)
                     throws DimensionMismatchException
```
Calculates the L₁ (sum of abs) distance between two points.

Parameters:
p1 - the first point
p2 - the second point

Returns:
the L₁ distance between the two points

Throws:

DimensionMismatchException - if the array lengths differ.

distance
```
public static double distance(double[] p1,
              double[] p2)
                       throws DimensionMismatchException
```
Calculates the L₂ (Euclidean) distance between two points.

Parameters:
p1 - the first point
p2 - the second point

Returns:
the L₂ distance between the two points

Throws:

DimensionMismatchException - if the array lengths differ.

cosAngle
```
public static double cosAngle(double[] v1,
              double[] v2)
```
Calculates the cosine of the angle between two vectors.

Parameters:
v1 - Cartesian coordinates of the first vector.
v2 - Cartesian coordinates of the second vector.

Returns:
the cosine of the angle between the vectors.
Since:

3.6

distance
```
public static double distance(int[] p1,
              int[] p2)
                       throws DimensionMismatchException
```
Calculates the L₂ (Euclidean) distance between two points.

Parameters:
p1 - the first point
p2 - the second point

Returns:
the L₂ distance between the two points

Throws:

DimensionMismatchException - if the array lengths differ.

distanceInf
```
public static double distanceInf(double[] p1,
                 double[] p2)
                          throws DimensionMismatchException
```
Calculates the L_∞ (max of abs) distance between two points.

Parameters:
p1 - the first point
p2 - the second point

Returns:
the L_∞ distance between the two points

Throws:

DimensionMismatchException - if the array lengths differ.

distanceInf
```
public static int distanceInf(int[] p1,
              int[] p2)
                       throws DimensionMismatchException
```
Calculates the L_∞ (max of abs) distance between two points.

Parameters:
p1 - the first point
p2 - the second point

Returns:
the L_∞ distance between the two points

Throws:

DimensionMismatchException - if the array lengths differ.

isMonotonic

public static <T extends Comparable<? super T>> boolean isMonotonic(T[] val,
                                                    MathArrays.OrderDirection dir,
                                                    boolean strict)

Check that an array is monotonically increasing or decreasing.

Type Parameters:: T - the type of the elements in the specified array
Parameters:: val - Values.; dir - Ordering direction.; strict - Whether the order should be strict.
Returns:: true if sorted, false otherwise.

isMonotonic
```
public static boolean isMonotonic(double[] val,
                  MathArrays.OrderDirection dir,
                  boolean strict)
```
Check that an array is monotonically increasing or decreasing.

Parameters:
val - Values.
dir - Ordering direction.
strict - Whether the order should be strict.

Returns:
true if sorted, false otherwise.

checkEqualLength
```
public static boolean checkEqualLength(double[] a,
                       double[] b,
                       boolean abort)
```
Check that both arrays have the same length.

Parameters:
a - Array.
b - Array.
abort - Whether to throw an exception if the check fails.

Returns:
true if the arrays have the same length.

Throws:

DimensionMismatchException - if the lengths differ and abort is true.
Since:

3.6

checkEqualLength
```
public static void checkEqualLength(double[] a,
                    double[] b)
```
Check that both arrays have the same length.

Parameters:
a - Array.
b - Array.

Throws:

DimensionMismatchException - if the lengths differ.
Since:

3.6

checkEqualLength
```
public static boolean checkEqualLength(int[] a,
                       int[] b,
                       boolean abort)
```
Check that both arrays have the same length.

Parameters:
a - Array.
b - Array.
abort - Whether to throw an exception if the check fails.

Returns:
true if the arrays have the same length.

Throws:

DimensionMismatchException - if the lengths differ and abort is true.
Since:

3.6

checkEqualLength
```
public static void checkEqualLength(int[] a,
                    int[] b)
```
Check that both arrays have the same length.

Parameters:
a - Array.
b - Array.

Throws:

DimensionMismatchException - if the lengths differ.
Since:

3.6

checkOrder
```
public static boolean checkOrder(double[] val,
                 MathArrays.OrderDirection dir,
                 boolean strict,
                 boolean abort)
                          throws NonMonotonicSequenceException
```
Check that the given array is sorted.

Parameters:
val - Values.
dir - Ordering direction.
strict - Whether the order should be strict.
abort - Whether to throw an exception if the check fails.

Returns:
true if the array is sorted.

Throws:

NonMonotonicSequenceException - if the array is not sorted and abort is true.

checkOrder
```
public static void checkOrder(double[] val,
              MathArrays.OrderDirection dir,
              boolean strict)
                       throws NonMonotonicSequenceException
```
Check that the given array is sorted.

Parameters:
val - Values.
dir - Ordering direction.
strict - Whether the order should be strict.

Throws:

NonMonotonicSequenceException - if the array is not sorted.
Since:

2.2

checkOrder
```
public static void checkOrder(double[] val)
                       throws NonMonotonicSequenceException
```
Check that the given array is sorted in strictly increasing order.

Parameters:
val - Values.

Throws:

NonMonotonicSequenceException - if the array is not sorted.
Since:

2.2

checkRectangular
```
public static void checkRectangular(long[][] in)
                             throws NullArgumentException,
                                    DimensionMismatchException
```
Throws DimensionMismatchException if the input array is not rectangular.

Parameters:
in - array to be tested

Throws:

NullArgumentException - if input array is null

DimensionMismatchException - if input array is not rectangular
Since:

3.1

checkPositive
```
public static void checkPositive(double[] in)
                          throws NotStrictlyPositiveException
```
Check that all entries of the input array are strictly positive.

Parameters:
in - Array to be tested

Throws:

NotStrictlyPositiveException - if any entries of the array are not strictly positive.
Since:

3.1

checkNotNaN
```
public static void checkNotNaN(double[] in)
                        throws NotANumberException
```
Check that no entry of the input array is NaN.

Parameters:
in - Array to be tested.

Throws:

NotANumberException - if an entry is NaN.
Since:

3.4

checkNonNegative
```
public static void checkNonNegative(long[] in)
                             throws NotPositiveException
```
Check that all entries of the input array are >= 0.

Parameters:
in - Array to be tested

Throws:

NotPositiveException - if any array entries are less than 0.
Since:

3.1

checkNonNegative
```
public static void checkNonNegative(long[][] in)
                             throws NotPositiveException
```
Check all entries of the input array are >= 0.

Parameters:
in - Array to be tested

Throws:

NotPositiveException - if any array entries are less than 0.
Since:

3.1

safeNorm

public static double safeNorm(double[] v)

Returns the Cartesian norm (2-norm), handling both overflow and underflow. Translation of the minpack enorm subroutine. The redistribution policy for MINPACK is available here, for convenience, it is reproduced below.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
The end-user documentation included with the redistribution, if any, must include the following acknowledgment: This product includes software developed by the University of Chicago, as Operator of Argonne National Laboratory. Alternately, this acknowledgment may appear in the software itself, if and wherever such third-party acknowledgments normally appear.
WARRANTY DISCLAIMER. THE SOFTWARE IS SUPPLIED "AS IS" WITHOUT WARRANTY OF ANY KIND. THE COPYRIGHT HOLDER, THE UNITED STATES, THE UNITED STATES DEPARTMENT OF ENERGY, AND THEIR EMPLOYEES: (1) DISCLAIM ANY WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE OR NON-INFRINGEMENT, (2) DO NOT ASSUME ANY LEGAL LIABILITY OR RESPONSIBILITY FOR THE ACCURACY, COMPLETENESS, OR USEFULNESS OF THE SOFTWARE, (3) DO NOT REPRESENT THAT USE OF THE SOFTWARE WOULD NOT INFRINGE PRIVATELY OWNED RIGHTS, (4) DO NOT WARRANT THAT THE SOFTWARE WILL FUNCTION UNINTERRUPTED, THAT IT IS ERROR-FREE OR THAT ANY ERRORS WILL BE CORRECTED.
LIMITATION OF LIABILITY. IN NO EVENT WILL THE COPYRIGHT HOLDER, THE UNITED STATES, THE UNITED STATES DEPARTMENT OF ENERGY, OR THEIR EMPLOYEES: BE LIABLE FOR ANY INDIRECT, INCIDENTAL, CONSEQUENTIAL, SPECIAL OR PUNITIVE DAMAGES OF ANY KIND OR NATURE, INCLUDING BUT NOT LIMITED TO LOSS OF PROFITS OR LOSS OF DATA, FOR ANY REASON WHATSOEVER, WHETHER SUCH LIABILITY IS ASSERTED ON THE BASIS OF CONTRACT, TORT (INCLUDING NEGLIGENCE OR STRICT LIABILITY), OR OTHERWISE, EVEN IF ANY OF SAID PARTIES HAS BEEN WARNED OF THE POSSIBILITY OF SUCH LOSS OR DAMAGES.

Parameters:: v - Vector of doubles.
Returns:: the 2-norm of the vector.
Since:: 2.2

sortInPlace
```
public static void sortInPlace(double[] x,
               double[]... yList)
                        throws DimensionMismatchException,
                               NullArgumentException
```
Sort an array in ascending order in place and perform the same reordering of entries on other arrays. For example, if x = [3, 1, 2], y = [1, 2, 3] and z = [0, 5, 7], then sortInPlace(x, y, z) will update x to [1, 2, 3], y to [2, 3, 1] and z to [5, 7, 0].

Parameters:
x - Array to be sorted and used as a pattern for permutation of the other arrays.
yList - Set of arrays whose permutations of entries will follow those performed on x.

Throws:

DimensionMismatchException - if any y is not the same size as x.

NullArgumentException - if x or any y is null.
Since:

3.0

sortInPlace
```
public static void sortInPlace(double[] x,
               MathArrays.OrderDirection dir,
               double[]... yList)
                        throws NullArgumentException,
                               DimensionMismatchException
```
Sort an array in place and perform the same reordering of entries on other arrays. This method works the same as the other sortInPlace method, but allows the order of the sort to be provided in the dir parameter.

Parameters:
x - Array to be sorted and used as a pattern for permutation of the other arrays.
dir - Order direction.
yList - Set of arrays whose permutations of entries will follow those performed on x.

Throws:

DimensionMismatchException - if any y is not the same size as x.

NullArgumentException - if x or any y is null
Since:

3.0

copyOf
```
public static int[] copyOf(int[] source)
```
Creates a copy of the source array.

Parameters:
source - Array to be copied.

Returns:
the copied array.

copyOf
```
public static double[] copyOf(double[] source)
```
Creates a copy of the source array.

Parameters:
source - Array to be copied.

Returns:
the copied array.

copyOf
```
public static int[] copyOf(int[] source,
           int len)
```
Creates a copy of the source array.

Parameters:
source - Array to be copied.
len - Number of entries to copy. If smaller then the source length, the copy will be truncated, if larger it will padded with zeroes.

Returns:
the copied array.

copyOf
```
public static double[] copyOf(double[] source,
              int len)
```
Creates a copy of the source array.

Parameters:
source - Array to be copied.
len - Number of entries to copy. If smaller then the source length, the copy will be truncated, if larger it will padded with zeroes.

Returns:
the copied array.

copyOfRange
```
public static double[] copyOfRange(double[] source,
                   int from,
                   int to)
```
Creates a copy of the source array.

Parameters:
source - Array to be copied.
from - Initial index of the range to be copied, inclusive.
to - Final index of the range to be copied, exclusive. (This index may lie outside the array.)

Returns:
the copied array.

linearCombination
```
public static double linearCombination(double[] a,
                       double[] b)
                                throws DimensionMismatchException
```
Compute a linear combination accurately. This method computes the sum of the products a_i b_i to high accuracy. It does so by using specific multiplication and addition algorithms to preserve accuracy and reduce cancellation effects.
It is based on the 2005 paper Accurate Sum and Dot Product by Takeshi Ogita, Siegfried M. Rump, and Shin'ichi Oishi published in SIAM J. Sci. Comput.

Parameters:
a - Factors.
b - Factors.

Returns:
Σ_i a_i b_i.

Throws:

DimensionMismatchException - if arrays dimensions don't match

linearCombination
```
public static double linearCombination(double a1,
                       double b1,
                       double a2,
                       double b2)
```
Compute a linear combination accurately.
This method computes a₁×b₁ + a₂×b₂ to high accuracy. It does so by using specific multiplication and addition algorithms to preserve accuracy and reduce cancellation effects. It is based on the 2005 paper Accurate Sum and Dot Product by Takeshi Ogita, Siegfried M. Rump, and Shin'ichi Oishi published in SIAM J. Sci. Comput.

Parameters:
a1 - first factor of the first term
b1 - second factor of the first term
a2 - first factor of the second term
b2 - second factor of the second term

Returns:
a₁×b₁ + a₂×b₂
See Also:
linearCombination(double, double, double, double, double, double), linearCombination(double, double, double, double, double, double, double, double)

linearCombination
```
public static double linearCombination(double a1,
                       double b1,
                       double a2,
                       double b2,
                       double a3,
                       double b3)
```
Compute a linear combination accurately.
This method computes a₁×b₁ + a₂×b₂ + a₃×b₃ to high accuracy. It does so by using specific multiplication and addition algorithms to preserve accuracy and reduce cancellation effects. It is based on the 2005 paper Accurate Sum and Dot Product by Takeshi Ogita, Siegfried M. Rump, and Shin'ichi Oishi published in SIAM J. Sci. Comput.

Parameters:
a1 - first factor of the first term
b1 - second factor of the first term
a2 - first factor of the second term
b2 - second factor of the second term
a3 - first factor of the third term
b3 - second factor of the third term

Returns:
a₁×b₁ + a₂×b₂ + a₃×b₃
See Also:
linearCombination(double, double, double, double), linearCombination(double, double, double, double, double, double, double, double)

linearCombination
```
public static double linearCombination(double a1,
                       double b1,
                       double a2,
                       double b2,
                       double a3,
                       double b3,
                       double a4,
                       double b4)
```
Compute a linear combination accurately.
This method computes a₁×b₁ + a₂×b₂ + a₃×b₃ + a₄×b₄ to high accuracy. It does so by using specific multiplication and addition algorithms to preserve accuracy and reduce cancellation effects. It is based on the 2005 paper Accurate Sum and Dot Product by Takeshi Ogita, Siegfried M. Rump, and Shin'ichi Oishi published in SIAM J. Sci. Comput.

Parameters:
a1 - first factor of the first term
b1 - second factor of the first term
a2 - first factor of the second term
b2 - second factor of the second term
a3 - first factor of the third term
b3 - second factor of the third term
a4 - first factor of the third term
b4 - second factor of the third term

Returns:
a₁×b₁ + a₂×b₂ + a₃×b₃ + a₄×b₄
See Also:
linearCombination(double, double, double, double), linearCombination(double, double, double, double, double, double)

equals
```
public static boolean equals(float[] x,
             float[] y)
```
Returns true iff both arguments are null or have same dimensions and all their elements are equal as defined by Precision.equals(float,float).

Parameters:
x - first array
y - second array

Returns:
true if the values are both null or have same dimension and equal elements.

equalsIncludingNaN
```
public static boolean equalsIncludingNaN(float[] x,
                         float[] y)
```
Returns true iff both arguments are null or have same dimensions and all their elements are equal as defined by this method.

Parameters:
x - first array
y - second array

Returns:
true if the values are both null or have same dimension and equal elements
Since:

2.2

equals
```
public static boolean equals(double[] x,
             double[] y)
```
Returns true iff both arguments are null or have same dimensions and all their elements are equal as defined by Precision.equals(double,double).

Parameters:
x - First array.
y - Second array.

Returns:
true if the values are both null or have same dimension and equal elements.

equalsIncludingNaN
```
public static boolean equalsIncludingNaN(double[] x,
                         double[] y)
```
Returns true iff both arguments are null or have same dimensions and all their elements are equal as defined by this method.

Parameters:
x - First array.
y - Second array.

Returns:
true if the values are both null or have same dimension and equal elements.
Since:

2.2

normalizeArray
```
public static double[] normalizeArray(double[] values,
                      double normalizedSum)
                               throws MathIllegalArgumentException,
                                      MathArithmeticException
```
Normalizes an array to make it sum to a specified value. Returns the result of the transformation
```
    x |-> x * normalizedSum / sum
 
```
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.
Throws IllegalArgumentException if normalizedSum is infinite or NaN and ArithmeticException if the input array contains any infinite elements or sums to 0.
Ignores (i.e., copies unchanged to the output array) NaNs in the input array.
Parameters:
values - Input array to be normalized
normalizedSum - Target sum for the normalized array

Returns:
the normalized array.

Throws:

MathArithmeticException - if the input array contains infinite elements or sums to zero.

MathIllegalArgumentException - if the target sum is infinite or NaN.
Since:

2.1

buildArray
```
public static <T> T[] buildArray(Field<T> field,
                 int length)
```
Build an array of elements.
Arrays are filled with field.getZero()

Type Parameters:
T - the type of the field elements
Parameters:
field - field to which array elements belong
length - of the array

Returns:
a new array
Since:

3.2

buildArray
```
public static <T> T[][] buildArray(Field<T> field,
                   int rows,
                   int columns)
```
Build a double dimension array of elements.
Arrays are filled with field.getZero()

Type Parameters:
T - the type of the field elements
Parameters:
field - field to which array elements belong
rows - number of rows in the array
columns - number of columns (may be negative to build partial arrays in the same way new Field[rows][] works)

Returns:
a new array
Since:

3.2

convolve
```
public static double[] convolve(double[] x,
                double[] h)
                         throws NullArgumentException,
                                NoDataException
```
Calculates the convolution between two sequences.
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.

Parameters:
x - First sequence. Typically, this sequence will represent an input signal to a system.
h - Second sequence. Typically, this sequence will represent the impulse response of the system.

Returns:
the convolution of x and h. This array's length will be x.length + h.length - 1.

Throws:

NullArgumentException - if either x or h is null.

NoDataException - if either x or h is empty.
Since:

3.3

shuffle
```
public static void shuffle(int[] list,
           int start,
           MathArrays.Position pos)
```
Shuffle the entries of the given array. The start and pos parameters select which portion of the array is randomized and which is left untouched.

Parameters:
list - Array whose entries will be shuffled (in-place).
start - Index at which shuffling begins.
pos - Shuffling is performed for index positions between start and either the end (if MathArrays.Position.TAIL) or the beginning (if MathArrays.Position.HEAD) of the array.
See Also:
shuffle(int[],int,Position,RandomGenerator)

shuffle
```
public static void shuffle(int[] list,
           int start,
           MathArrays.Position pos,
           RandomGenerator rng)
```
Shuffle the entries of the given array, using the Fisher–Yates algorithm. The start and pos parameters select which portion of the array is randomized and which is left untouched.

Parameters:
list - Array whose entries will be shuffled (in-place).
start - Index at which shuffling begins.
pos - Shuffling is performed for index positions between start and either the end (if MathArrays.Position.TAIL) or the beginning (if MathArrays.Position.HEAD) of the array.
rng - Random number generator.

shuffle
```
public static void shuffle(int[] list,
           RandomGenerator rng)
```
Shuffle the entries of the given array.

Parameters:
list - Array whose entries will be shuffled (in-place).
rng - Random number generator.
See Also:
shuffle(int[],int,Position,RandomGenerator)

shuffle
```
public static void shuffle(int[] list)
```
Shuffle the entries of the given array.

Parameters:
list - Array whose entries will be shuffled (in-place).
See Also:
shuffle(int[],int,Position,RandomGenerator)

natural
```
public static int[] natural(int n)
```
Returns an array representing the natural number n.

Parameters:
n - Natural number.

Returns:
an array whose entries are the numbers 0, 1, ..., n-1. If n == 0, the returned array is empty.

sequence
```
public static int[] sequence(int size,
             int start,
             int stride)
```
Returns an array of size integers starting at start, skipping stride numbers.

Parameters:
size - Natural number.
start - Natural number.
stride - Natural number.

Returns:
an array whose entries are the numbers start, start + stride, ..., start + (size - 1) * stride. If size == 0, the returned array is empty.
Since:

3.4

verifyValues
```
public static boolean verifyValues(double[] values,
                   int begin,
                   int length)
                            throws MathIllegalArgumentException
```
This method is used to verify that the input parameters designate a subarray of positive length.
- returns true iff the parameters designate a subarray of positive length
- throws MathIllegalArgumentException if the array is null or or the indices are invalid
- returns false
Parameters: values - the input array begin - index of the first array element to include length - the number of elements to include Returns: 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







verifyValues
public static boolean verifyValues(double[] values,
                   int begin,
                   int length,
                   boolean allowEmpty)
                            throws MathIllegalArgumentException
This method is used
 to verify that the input parameters designate a subarray of positive length.
 
 

 returns true iff the parameters designate a subarray of
 non-negative length
 throws IllegalArgumentException if the array is null or
 or the indices are invalid
 returns false
 if the array is non-null, but
 length is 0 unless allowEmpty is true
 

Parameters:
values - the input array
begin - index of the first array element to include
length - the number of elements to include
allowEmpty - if true then zero length arrays are allowed
Returns:
true if the parameters are valid
Throws:
MathIllegalArgumentException - if the indices are invalid or the array is null
Since:
  3.3







verifyValues
public static boolean verifyValues(double[] values,
                   double[] weights,
                   int begin,
                   int length)
                            throws MathIllegalArgumentException
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.
 
 

 returns true iff the parameters designate a subarray of
 positive length and the weights array contains legitimate values.
 throws IllegalArgumentException if any of the following are true:
 the values array is null
     the weights array is null
     the weights array does not have the same length as the values array
     the weights array contains one or more infinite values
     the weights array contains one or more NaN values
     the weights array contains negative values
     the start and length arguments do not determine a valid array
 
 returns false
 if the array is non-null, but
 length is 0.
 

Parameters:
values - the input array
weights - the weights array
begin - index of the first array element to include
length - the number of elements to include
Returns:
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







verifyValues
public static boolean verifyValues(double[] values,
                   double[] weights,
                   int begin,
                   int length,
                   boolean allowEmpty)
                            throws MathIllegalArgumentException
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.
 
 

 returns true iff the parameters designate a subarray of
 non-negative length and the weights array contains legitimate values.
 throws MathIllegalArgumentException if any of the following are true:
 the values array is null
     the weights array is null
     the weights array does not have the same length as the values array
     the weights array contains one or more infinite values
     the weights array contains one or more NaN values
     the weights array contains negative values
     the start and length arguments do not determine a valid array
 
 returns false
 if the array is non-null, but
 length is 0 unless allowEmpty is true.
 

Parameters:
values - the input array.
weights - the weights array.
begin - index of the first array element to include.
length - the number of elements to include.
allowEmpty - if true than allow zero length arrays to pass.
Returns:
true if the parameters are valid.
Throws:
NullArgumentException - if either of the arrays are null
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







concatenate
public static double[] concatenate(double[]... x)
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).
Parameters:
x - list of double[] arrays to concatenate
Returns:
a new array consisting of the entries of the argument arrays
Throws:
NullPointerException - if any of the arrays are null
Since:
  3.6







unique
public static double[] unique(double[] data)
Returns an array consisting of the unique values in 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 data,
 Double.NaN will be the first element of the output array,
 even if the array also contains Double.POSITIVE_INFINITY.
Parameters:
data - array to scan
Returns:
descending list of values included in the input array
Throws:
NullPointerException - if data is null
Since:
  3.6

Class MathArrays

Nested Class Summary

Method Summary

Methods inherited from class java.lang.Object

Method Detail

scale

scaleInPlace

ebeAdd

ebeSubtract

ebeMultiply

ebeDivide

distance1

distance1

distance

cosAngle

distance

distanceInf

distanceInf

isMonotonic

isMonotonic

checkEqualLength

checkEqualLength

checkEqualLength

checkEqualLength

checkOrder

checkOrder

checkOrder

checkRectangular

checkPositive

checkNotNaN

checkNonNegative

checkNonNegative

safeNorm

sortInPlace

sortInPlace

copyOf

copyOf

copyOf

copyOf

copyOfRange

linearCombination

linearCombination

linearCombination

linearCombination

equals

equalsIncludingNaN

equals

equalsIncludingNaN

normalizeArray

buildArray

buildArray

convolve

shuffle

shuffle

shuffle

shuffle

natural

sequence

verifyValues

verifyValues

verifyValues

verifyValues

concatenate

unique