## org.apache.commons.math.linear
Class SparseFieldVector<T extends FieldElement<T>>

    java.lang.Object
      org.apache.commons.math.linear.SparseFieldVector<T>

Type Parameters:
  `T` - the type of the field elements

All Implemented Interfaces:
  java.io.Serializable, FieldVector<T>

    public class SparseFieldVector<T extends FieldElement<T>>

extends java.lang.Object
implements FieldVector<T>, java.io.Serializable

This class implements the `FieldVector` interface with a `OpenIntToFieldHashMap` backing store.

Since:
  2.0
Version:
  $Revision: 922714 $ $Date: 2010-03-13 20:35:14 -0500 (Sat, 13 Mar 2010) $
See Also:
  Serialized Form

Field Summary
`private OpenIntToFieldHashMap<T>` `entries` Entries of the vector.
`private Field<T>` `field` Field to which the elements belong.
`private static long` `serialVersionUID` Serial version id
`private int` `virtualSize` Dimension of the vector.

Constructor Summary
`` `SparseFieldVector(Field<T> field)` Build a 0-length vector.
`` `SparseFieldVector(Field<T> field, int dimension)` Construct a (dimension)-length vector of zeros.
`` `SparseFieldVector(Field<T> field, int dimension, int expectedSize)` Build a vector with known the sparseness (for advanced use only).
`` `SparseFieldVector(Field<T> field, T[] values)` Create from a Field array.
`` `SparseFieldVector(SparseFieldVector<T> v)` Copy constructor.
`protected` `SparseFieldVector(SparseFieldVector<T> v, int resize)` Build a resized vector, for use with append.

Method Summary
`FieldVector<T>` `add(FieldVector<T> v)` Compute the sum of this and v.
`FieldVector<T>` `add(SparseFieldVector<T> v)` Optimized method to add sparse vectors.
`FieldVector<T>` `add(T[] v)` Compute the sum of this and v.
`FieldVector<T>` `append(FieldVector<T> v)` Construct a vector by appending a vector to this vector.
`FieldVector<T>` `append(SparseFieldVector<T> v)` Construct a vector by appending a vector to this vector.
`FieldVector<T>` `append(T d)` Construct a vector by appending a T to this vector.
`FieldVector<T>` `append(T[] a)` Construct a vector by appending a T array to this vector.
`private T[]` `buildArray(int length)` Build an array of elements.
`private void` `checkIndex(int index)` Check if an index is valid.
`protected void` `checkVectorDimensions(int n)` Check if instance dimension is equal to some expected value.
`FieldVector<T>` `copy()` Returns a (deep) copy of this.
`T` `dotProduct(FieldVector<T> v)` Compute the dot product.
`T` `dotProduct(T[] v)` Compute the dot product.
`FieldVector<T>` `ebeDivide(FieldVector<T> v)` Element-by-element division.
`FieldVector<T>` `ebeDivide(T[] v)` Element-by-element division.
`FieldVector<T>` `ebeMultiply(FieldVector<T> v)` Element-by-element multiplication.
`FieldVector<T>` `ebeMultiply(T[] v)` Element-by-element multiplication.
`boolean` `equals(java.lang.Object obj)`
`T[]` `getData()` Returns vector entries as a T array.
`int` `getDimension()` Returns the size of the vector.
`private OpenIntToFieldHashMap<T>` `getEntries()` Get the entries of this instance.
`T` `getEntry(int index)` Returns the entry in the specified index.
`Field<T>` `getField()` Get the type of field elements of the vector.
`FieldVector<T>` `getSubVector(int index, int n)` Get a subvector from consecutive elements.
`int` `hashCode()`
`FieldVector<T>` `mapAdd(T d)` Map an addition operation to each entry.
`FieldVector<T>` `mapAddToSelf(T d)` Map an addition operation to each entry.
`FieldVector<T>` `mapDivide(T d)` Map a division operation to each entry.
`FieldVector<T>` `mapDivideToSelf(T d)` Map a division operation to each entry.
`FieldVector<T>` `mapInv()` Map the 1/x function to each entry.
`FieldVector<T>` `mapInvToSelf()` Map the 1/x function to each entry.
`FieldVector<T>` `mapMultiply(T d)` Map a multiplication operation to each entry.
`FieldVector<T>` `mapMultiplyToSelf(T d)` Map a multiplication operation to each entry.
`FieldVector<T>` `mapSubtract(T d)` Map a subtraction operation to each entry.
`FieldVector<T>` `mapSubtractToSelf(T d)` Map a subtraction operation to each entry.
`FieldMatrix<T>` `outerProduct(FieldVector<T> v)` Compute the outer product.
`FieldMatrix<T>` `outerProduct(SparseFieldVector<T> v)` Optimized method to compute outer product when both vectors are sparse.
`FieldMatrix<T>` `outerProduct(T[] v)` Compute the outer product.
`FieldVector<T>` `projection(FieldVector<T> v)` Find the orthogonal projection of this vector onto another vector.
`FieldVector<T>` `projection(T[] v)` Find the orthogonal projection of this vector onto another vector.
`void` `set(T value)` Set all elements to a single value.
`void` `setEntry(int index, T value)` Set a single element.
`void` `setSubVector(int index, FieldVector<T> v)` Set a set of consecutive elements.
`void` `setSubVector(int index, T[] v)` Set a set of consecutive elements.
`FieldVector<T>` `subtract(FieldVector<T> v)` Compute this minus v.
`SparseFieldVector<T>` `subtract(SparseFieldVector<T> v)` Optimized method to subtract SparseRealVectors.
`FieldVector<T>` `subtract(T[] v)` Compute this minus v.
`T[]` `toArray()` Convert the vector to a T array.

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

Field Detail

### serialVersionUID

    private static final long serialVersionUID

  Serial version id

  See Also:
    Constant Field Values

### field

    private final Field<T extends FieldElement<T>> field

  Field to which the elements belong.

### entries

    private final OpenIntToFieldHashMap<T extends FieldElement<T>> entries

  Entries of the vector.

### virtualSize

    private final int virtualSize

  Dimension of the vector.

Constructor Detail

### SparseFieldVector

    public SparseFieldVector(Field<T> field)

  Build a 0-length vector.

  Zero-length vectors may be used to initialize construction of vectors by data gathering. We start with zero-length and use either the `SparseFieldVector(SparseFieldVector, int)` constructor or one of the `append` method (`append(FieldElement)`, `append(FieldElement[])`, `append(FieldVector)`, `append(SparseFieldVector)`) to gather data into this vector.

  Parameters:
    `field` - field to which the elements belong

### SparseFieldVector

    public SparseFieldVector(Field<T> field,
                             int dimension)

  Construct a (dimension)-length vector of zeros.

  Parameters:
    `field` - field to which the elements belong
    `dimension` - Size of the vector

### SparseFieldVector

    protected SparseFieldVector(SparseFieldVector<T> v,
                                int resize)

  Build a resized vector, for use with append.

  Parameters:
    `v` - The original vector
    `resize` - The amount to resize it

### SparseFieldVector

    public SparseFieldVector(Field<T> field,
                             int dimension,
                             int expectedSize)

  Build a vector with known the sparseness (for advanced use only).

  Parameters:
    `field` - field to which the elements belong
    `dimension` - The size of the vector
    `expectedSize` - The expected number of non-zero entries

### SparseFieldVector

    public SparseFieldVector(Field<T> field,
                             T[] values)

  Create from a Field array. Only non-zero entries will be stored

  Parameters:
    `field` - field to which the elements belong
    `values` - The set of values to create from

### SparseFieldVector

    public SparseFieldVector(SparseFieldVector<T> v)

  Copy constructor.

  Parameters:
    `v` - The instance to copy from

Method Detail

### getEntries

    private OpenIntToFieldHashMap<T> getEntries()

  Get the entries of this instance.

  Returns:
    entries of this instance

### add

    public FieldVector<T> add(SparseFieldVector<T> v)
                                               throws java.lang.IllegalArgumentException

  Optimized method to add sparse vectors.

  Parameters:
    `v` - vector to add
  Returns:
    The sum of `this` and `v`
  Throws:
    `java.lang.IllegalArgumentException` - If the dimensions don't match

### add

    public FieldVector<T> add(T[] v)
                                               throws java.lang.IllegalArgumentException

  Compute the sum of this and v.

  Specified by:
    `add` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector to be added
  Returns:
    this + v
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### append

    public FieldVector<T> append(SparseFieldVector<T> v)

  Construct a vector by appending a vector to this vector.

  Parameters:
    `v` - vector to append to this one.
  Returns:
    a new vector

### append

    public FieldVector<T> append(FieldVector<T> v)

  Construct a vector by appending a vector to this vector.

  Specified by:
    `append` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector to append to this one.
  Returns:
    a new vector

### append

    public FieldVector<T> append(T d)

  Construct a vector by appending a T to this vector.

  Specified by:
    `append` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `d` - T to append.
  Returns:
    a new vector

### append

    public FieldVector<T> append(T[] a)

  Construct a vector by appending a T array to this vector.

  Specified by:
    `append` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `a` - T array to append.
  Returns:
    a new vector

### copy

    public FieldVector<T> copy()

  Returns a (deep) copy of this.

  Specified by:
    `copy` in interface `FieldVector<T extends FieldElement<T>>`
  Returns:
    vector copy

### dotProduct

    public T dotProduct(FieldVector<T> v)
                                         throws java.lang.IllegalArgumentException

  Compute the dot product.

  Specified by:
    `dotProduct` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector with which dot product should be computed
  Returns:
    the scalar dot product between instance and v
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### dotProduct

    public T dotProduct(T[] v)
                                         throws java.lang.IllegalArgumentException

  Compute the dot product.

  Specified by:
    `dotProduct` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector with which dot product should be computed
  Returns:
    the scalar dot product between instance and v
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### ebeDivide

    public FieldVector<T> ebeDivide(FieldVector<T> v)
                                                     throws java.lang.IllegalArgumentException

  Element-by-element division.

  Specified by:
    `ebeDivide` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector by which instance elements must be divided
  Returns:
    a vector containing this[i] / v[i] for all i
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### ebeDivide

    public FieldVector<T> ebeDivide(T[] v)
                                                     throws java.lang.IllegalArgumentException

  Element-by-element division.

  Specified by:
    `ebeDivide` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector by which instance elements must be divided
  Returns:
    a vector containing this[i] / v[i] for all i
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### ebeMultiply

    public FieldVector<T> ebeMultiply(FieldVector<T> v)
                                                       throws java.lang.IllegalArgumentException

  Element-by-element multiplication.

  Specified by:
    `ebeMultiply` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector by which instance elements must be multiplied
  Returns:
    a vector containing this[i] * v[i] for all i
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### ebeMultiply

    public FieldVector<T> ebeMultiply(T[] v)
                                                       throws java.lang.IllegalArgumentException

  Element-by-element multiplication.

  Specified by:
    `ebeMultiply` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector by which instance elements must be multiplied
  Returns:
    a vector containing this[i] * v[i] for all i
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### getData

    public T[] getData()

  Returns vector entries as a T array.

  Specified by:
    `getData` in interface `FieldVector<T extends FieldElement<T>>`
  Returns:
    T array of entries

### getDimension

    public int getDimension()

  Returns the size of the vector.

  Specified by:
    `getDimension` in interface `FieldVector<T extends FieldElement<T>>`
  Returns:
    size

### getEntry

    public T getEntry(int index)
                                       throws MatrixIndexException

  Returns the entry in the specified index.

  The index start at 0 and must be lesser than the size, otherwise a `MatrixIndexException` is thrown.

  Specified by:
    `getEntry` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `index` - index location of entry to be fetched
  Returns:
    vector entry at index
  Throws:
    `MatrixIndexException` - if the index is not valid
  See Also:
    `FieldVector.setEntry(int, FieldElement)`

### getField

    public Field<T> getField()

  Get the type of field elements of the vector.

  Specified by:
    `getField` in interface `FieldVector<T extends FieldElement<T>>`
  Returns:
    type of field elements of the vector

### getSubVector

    public FieldVector<T> getSubVector(int index,
                                       int n)
                                                        throws MatrixIndexException

  Get a subvector from consecutive elements.

  Specified by:
    `getSubVector` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `index` - index of first element.
    `n` - number of elements to be retrieved.
  Returns:
    a vector containing n elements.
  Throws:
    `MatrixIndexException` - if the index is inconsistent with vector size

### mapAdd

    public FieldVector<T> mapAdd(T d)

  Map an addition operation to each entry.

  Specified by:
    `mapAdd` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `d` - value to be added to each entry
  Returns:
    this + d

### mapAddToSelf

    public FieldVector<T> mapAddToSelf(T d)

  Map an addition operation to each entry.

  The instance is changed by this method.

  Specified by:
    `mapAddToSelf` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `d` - value to be added to each entry
  Returns:
    for convenience, return this

### mapDivide

    public FieldVector<T> mapDivide(T d)

  Map a division operation to each entry.

  Specified by:
    `mapDivide` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `d` - value to divide all entries by
  Returns:
    this / d

### mapDivideToSelf

    public FieldVector<T> mapDivideToSelf(T d)

  Map a division operation to each entry.

  The instance is changed by this method.

  Specified by:
    `mapDivideToSelf` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `d` - value to divide all entries by
  Returns:
    for convenience, return this

### mapInv

    public FieldVector<T> mapInv()

  Map the 1/x function to each entry.

  Specified by:
    `mapInv` in interface `FieldVector<T extends FieldElement<T>>`
  Returns:
    a vector containing the result of applying the function to each entry

### mapInvToSelf

    public FieldVector<T> mapInvToSelf()

  Map the 1/x function to each entry.

  The instance is changed by this method.

  Specified by:
    `mapInvToSelf` in interface `FieldVector<T extends FieldElement<T>>`
  Returns:
    for convenience, return this

### mapMultiply

    public FieldVector<T> mapMultiply(T d)

  Map a multiplication operation to each entry.

  Specified by:
    `mapMultiply` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `d` - value to multiply all entries by
  Returns:
    this * d

### mapMultiplyToSelf

    public FieldVector<T> mapMultiplyToSelf(T d)

  Map a multiplication operation to each entry.

  The instance is changed by this method.

  Specified by:
    `mapMultiplyToSelf` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `d` - value to multiply all entries by
  Returns:
    for convenience, return this

### mapSubtract

    public FieldVector<T> mapSubtract(T d)

  Map a subtraction operation to each entry.

  Specified by:
    `mapSubtract` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `d` - value to be subtracted to each entry
  Returns:
    this - d

### mapSubtractToSelf

    public FieldVector<T> mapSubtractToSelf(T d)

  Map a subtraction operation to each entry.

  The instance is changed by this method.

  Specified by:
    `mapSubtractToSelf` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `d` - value to be subtracted to each entry
  Returns:
    for convenience, return this

### outerProduct

    public FieldMatrix<T> outerProduct(SparseFieldVector<T> v)
                                                        throws java.lang.IllegalArgumentException

  Optimized method to compute outer product when both vectors are sparse.

  Parameters:
    `v` - vector with which outer product should be computed
  Returns:
    the square matrix outer product between instance and v
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as `this`

### outerProduct

    public FieldMatrix<T> outerProduct(T[] v)
                                                        throws java.lang.IllegalArgumentException

  Compute the outer product.

  Specified by:
    `outerProduct` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector with which outer product should be computed
  Returns:
    the square matrix outer product between instance and v
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### outerProduct

    public FieldMatrix<T> outerProduct(FieldVector<T> v)
                                                        throws java.lang.IllegalArgumentException

  Compute the outer product.

  Specified by:
    `outerProduct` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector with which outer product should be computed
  Returns:
    the square matrix outer product between instance and v
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### projection

    public FieldVector<T> projection(FieldVector<T> v)
                                                      throws java.lang.IllegalArgumentException

  Find the orthogonal projection of this vector onto another vector.

  Specified by:
    `projection` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector onto which instance must be projected
  Returns:
    projection of the instance onto v
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### projection

    public FieldVector<T> projection(T[] v)
                                                      throws java.lang.IllegalArgumentException

  Find the orthogonal projection of this vector onto another vector.

  Specified by:
    `projection` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector onto which instance must be projected
  Returns:
    projection of the instance onto v
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### set

    public void set(T value)

  Set all elements to a single value.

  Specified by:
    `set` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `value` - single value to set for all elements

### setEntry

    public void setEntry(int index,
                         T value)
                  throws MatrixIndexException

  Set a single element.

  Specified by:
    `setEntry` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `index` - element index.
    `value` - new value for the element.
  Throws:
    `MatrixIndexException` - if the index is inconsistent with vector size
  See Also:
    `FieldVector.getEntry(int)`

### setSubVector

    public void setSubVector(int index,
                             FieldVector<T> v)
                      throws MatrixIndexException

  Set a set of consecutive elements.

  Specified by:
    `setSubVector` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `index` - index of first element to be set.
    `v` - vector containing the values to set.
  Throws:
    `MatrixIndexException` - if the index is inconsistent with vector size
  See Also:
    `FieldVector.setSubVector(int, FieldElement[])`

### setSubVector

    public void setSubVector(int index,
                             T[] v)
                      throws MatrixIndexException

  Set a set of consecutive elements.

  Specified by:
    `setSubVector` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `index` - index of first element to be set.
    `v` - vector containing the values to set.
  Throws:
    `MatrixIndexException` - if the index is inconsistent with vector size
  See Also:
    `FieldVector.setSubVector(int, FieldVector)`

### subtract

    public SparseFieldVector<T> subtract(SparseFieldVector<T> v)
                                                          throws java.lang.IllegalArgumentException

  Optimized method to subtract SparseRealVectors.

  Parameters:
    `v` - The vector to subtract from `this`
  Returns:
    The difference of `this` and `v`
  Throws:
    `java.lang.IllegalArgumentException` - If the dimensions don't match

### subtract

    public FieldVector<T> subtract(FieldVector<T> v)
                                                    throws java.lang.IllegalArgumentException

  Compute this minus v.

  Specified by:
    `subtract` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector to be subtracted
  Returns:
    this + v
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### subtract

    public FieldVector<T> subtract(T[] v)
                                                    throws java.lang.IllegalArgumentException

  Compute this minus v.

  Specified by:
    `subtract` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector to be subtracted
  Returns:
    this + v
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### toArray

    public T[] toArray()

  Convert the vector to a T array.

  The array is independent from vector data, it's elements are copied.

  Specified by:
    `toArray` in interface `FieldVector<T extends FieldElement<T>>`
  Returns:
    array containing a copy of vector elements

### checkIndex

    private void checkIndex(int index)
                     throws MatrixIndexException

  Check if an index is valid.

  Parameters:
    `index` - index to check
  Throws:
    `MatrixIndexException` - if index is not valid

### checkVectorDimensions

    protected void checkVectorDimensions(int n)
                                  throws java.lang.IllegalArgumentException

  Check if instance dimension is equal to some expected value.

  Parameters:
    `n` - expected dimension.
  Throws:
    `java.lang.IllegalArgumentException` - if the dimension is inconsistent with vector size

### add

    public FieldVector<T> add(FieldVector<T> v)
                                               throws java.lang.IllegalArgumentException

  Compute the sum of this and v.

  Specified by:
    `add` in interface `FieldVector<T extends FieldElement<T>>`
  Parameters:
    `v` - vector to be added
  Returns:
    this + v
  Throws:
    `java.lang.IllegalArgumentException` - if v is not the same size as this

### buildArray

    private T[] buildArray(int length)

  Build an array of elements.

  Parameters:
    `length` - size of the array to build
  Returns:
    a new array

### hashCode

    public int hashCode()

  Overrides:
    `hashCode` in class `java.lang.Object`

### equals

    public boolean equals(java.lang.Object obj)

  Overrides:
    `equals` in class `java.lang.Object`

Copyright (c) 2003-2010 Apache Software Foundation