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:
  Serializable, FieldVector<T>

    public class SparseFieldVector<T extends FieldElement<T>>
    extends Object
    implements FieldVector<T>, Serializable

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

Since:
  2.0
Version:
  $Revision: 983921 $ $Date: 2010-08-10 12:46:06 +0200 (mar. 10 août 2010) $
See Also:
  Serialized Form

### Field Summary

Fields
`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

Constructors
`` `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

Methods
`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(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 IllegalArgumentException

Optimized method to add sparse vectors.

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

#### add

    public FieldVector<T> add(T[] v)
                                               throws 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:
  `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 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:
  `IllegalArgumentException` - if v is not the same size as this

#### dotProduct

    public T dotProduct(T[] v)
                                         throws 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:
  `IllegalArgumentException` - if v is not the same size as this

#### ebeDivide

    public FieldVector<T> ebeDivide(FieldVector<T> v)
                                                     throws 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:
  `IllegalArgumentException` - if v is not the same size as this

#### ebeDivide

    public FieldVector<T> ebeDivide(T[] v)
                                                     throws 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:
  `IllegalArgumentException` - if v is not the same size as this

#### ebeMultiply

    public FieldVector<T> ebeMultiply(FieldVector<T> v)
                                                       throws 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:
  `IllegalArgumentException` - if v is not the same size as this

#### ebeMultiply

    public FieldVector<T> ebeMultiply(T[] v)
                                                       throws 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:
  `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 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:
  `IllegalArgumentException` - if v is not the same size as `this`

#### outerProduct

    public FieldMatrix<T> outerProduct(T[] v)
                                                        throws 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:
  `IllegalArgumentException` - if v is not the same size as this

#### outerProduct

    public FieldMatrix<T> outerProduct(FieldVector<T> v)
                                                        throws 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:
  `IllegalArgumentException` - if v is not the same size as this

#### projection

    public FieldVector<T> projection(FieldVector<T> v)
                                                      throws 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:
  `IllegalArgumentException` - if v is not the same size as this

#### projection

    public FieldVector<T> projection(T[] v)
                                                      throws 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:
  `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 IllegalArgumentException

Optimized method to subtract SparseRealVectors.

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

#### subtract

    public FieldVector<T> subtract(FieldVector<T> v)
                                                    throws 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:
  `IllegalArgumentException` - if v is not the same size as this

#### subtract

    public FieldVector<T> subtract(T[] v)
                                                    throws 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:
  `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 IllegalArgumentException

Check if instance dimension is equal to some expected value.

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

#### add

    public FieldVector<T> add(FieldVector<T> v)
                                               throws 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:
  `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 `Object`

#### equals

    public boolean equals(Object obj)

Overrides:
  `equals` in class `Object`