Package org.hipparchus.linear

Class RealVector

java.lang.Object
org.hipparchus.linear.RealVector
Direct Known Subclasses:
ArrayRealVector, SparseRealVector
public abstract class RealVector extends Object
Class defining a real-valued vector with basic algebraic operations.

vector element indexing is 0-based -- e.g., getEntry(0) returns the first element of the vector.

The code map and mapToSelf methods operate on vectors element-wise, i.e. they perform the same operation (adding a scalar, applying a function ...) on each element in turn. The map versions create a new vector to hold the result and do not change the instance. The mapToSelf version uses the instance itself to store the results, so the instance is changed by this method. In all cases, the result vector is returned by the methods, allowing the fluent API style, like this: 

   RealVector result = v.mapAddToSelf(3.4).mapToSelf(new Tan()).mapToSelf(new Power(2.3));

  • Constructor Details

    • RealVector

      public RealVector()
      Empty constructor.

      This constructor is not strictly necessary, but it prevents spurious javadoc warnings with JDK 18 and later.

      Since:
      3.0

  • Method Details

    • getDimension

      public abstract int getDimension()
      Returns the size of the vector.
      Returns:
      the size of this vector.

    • getEntry

      public abstract double getEntry(int index) throws MathIllegalArgumentException
      Return the entry at the specified index.
      Parameters:
      index - Index location of entry to be fetched.
      Returns:
      the vector entry at index.
      Throws:
      MathIllegalArgumentException - if the index is not valid.
      See Also:

    • setEntry

      public abstract void setEntry(int index, double value) throws MathIllegalArgumentException
      Set a single element.
      Parameters:
      index - element index.
      value - new value for the element.
      Throws:
      MathIllegalArgumentException - if the index is not valid.
      See Also:

    • addToEntry

      public void addToEntry(int index, double increment) throws MathIllegalArgumentException
      Change an entry at the specified index.
      Parameters:
      index - Index location of entry to be set.
      increment - Value to add to the vector entry.
      Throws:
      MathIllegalArgumentException - if the index is not valid.

    • append

      public abstract RealVector append(RealVector v)
      Construct a new vector by appending a vector to this vector.
      Parameters:
      v - vector to append to this one.
      Returns:
      a new vector.

    • append

      public abstract RealVector append(double d)
      Construct a new vector by appending a double to this vector.
      Parameters:
      d - double to append.
      Returns:
      a new vector.

    • getSubVector

      public abstract RealVector getSubVector(int index, int n) throws MathIllegalArgumentException
      Get a subvector from consecutive elements.
      Parameters:
      index - index of first element.
      n - number of elements to be retrieved.
      Returns:
      a vector containing n elements.
      Throws:
      MathIllegalArgumentException - if the index is not valid.
      MathIllegalArgumentException - if the number of elements is not positive.

    • setSubVector

      public abstract void setSubVector(int index, RealVector v) throws MathIllegalArgumentException
      Set a sequence of consecutive elements.
      Parameters:
      index - index of first element to be set.
      v - vector containing the values to set.
      Throws:
      MathIllegalArgumentException - if the index is not valid.

    • isNaN

      public abstract boolean isNaN()
      Check whether any coordinate of this vector is NaN.
      Returns:
      true if any coordinate of this vector is NaN, false otherwise.

    • isInfinite

      public abstract boolean isInfinite()
      Check whether any coordinate of this vector is infinite and none are NaN.
      Returns:
      true if any coordinate of this vector is infinite and none are NaN, false otherwise.

    • checkVectorDimensions

      protected void checkVectorDimensions(RealVector v) throws MathIllegalArgumentException
      Check if instance and specified vectors have the same dimension.
      Parameters:
      v - Vector to compare instance with.
      Throws:
      MathIllegalArgumentException - if the vectors do not have the same dimension.

    • checkVectorDimensions

      protected void checkVectorDimensions(int n) throws MathIllegalArgumentException
      Check if instance dimension is equal to some expected value.
      Parameters:
      n - Expected dimension.
      Throws:
      MathIllegalArgumentException - if the dimension is inconsistent with the vector size.

    • checkIndex

      protected void checkIndex(int index) throws MathIllegalArgumentException
      Check if an index is valid.
      Parameters:
      index - Index to check.
      Throws:
      MathIllegalArgumentException - if index is not valid.

    • checkIndices

      protected void checkIndices(int start, int end) throws MathIllegalArgumentException
      Checks that the indices of a subvector are valid.
      Parameters:
      start - the index of the first entry of the subvector
      end - the index of the last entry of the subvector (inclusive)
      Throws:
      MathIllegalArgumentException - if start of end are not valid
      MathIllegalArgumentException - if end < start

    • add

      public RealVector add(RealVector v) throws MathIllegalArgumentException
      Compute the sum of this vector and v. Returns a new vector. Does not change instance data.
      Parameters:
      v - Vector to be added.
      Returns:
      this + v.
      Throws:
      MathIllegalArgumentException - if v is not the same size as this vector.

    • subtract

      public RealVector subtract(RealVector v) throws MathIllegalArgumentException
      Subtract v from this vector. Returns a new vector. Does not change instance data.
      Parameters:
      v - Vector to be subtracted.
      Returns:
      this - v.
      Throws:
      MathIllegalArgumentException - if v is not the same size as this vector.

    • mapAdd

      public RealVector mapAdd(double d)
      Add a value to each entry. Returns a new vector. Does not change instance data.
      Parameters:
      d - Value to be added to each entry.
      Returns:
      this + d.

    • mapAddToSelf

      public RealVector mapAddToSelf(double d)
      Add a value to each entry. The instance is changed in-place.
      Parameters:
      d - Value to be added to each entry.
      Returns:
      this.

    • copy

      public abstract RealVector copy()
      Returns a (deep) copy of this vector.
      Returns:
      a vector copy.

    • dotProduct

      public double dotProduct(RealVector v) throws MathIllegalArgumentException
      Compute the dot product of this vector with v.
      Parameters:
      v - Vector with which dot product should be computed
      Returns:
      the scalar dot product between this instance and v.
      Throws:
      MathIllegalArgumentException - if v is not the same size as this vector.

    • cosine

      public double cosine(RealVector v) throws MathIllegalArgumentException, MathRuntimeException
      Computes the cosine of the angle between this vector and the argument.
      Parameters:
      v - Vector.
      Returns:
      the cosine of the angle between this vector and v.
      Throws:
      MathRuntimeException - if this or v is the null vector
      MathIllegalArgumentException - if the dimensions of this and v do not match

    • ebeDivide

      public abstract RealVector ebeDivide(RealVector v) throws MathIllegalArgumentException
      Element-by-element division.
      Parameters:
      v - Vector by which instance elements must be divided.
      Returns:
      a vector containing this[i] / v[i] for all i.
      Throws:
      MathIllegalArgumentException - if v is not the same size as this vector.

    • ebeMultiply

      public abstract RealVector ebeMultiply(RealVector v) throws MathIllegalArgumentException
      Element-by-element multiplication.
      Parameters:
      v - Vector by which instance elements must be multiplied
      Returns:
      a vector containing this[i] * v[i] for all i.
      Throws:
      MathIllegalArgumentException - if v is not the same size as this vector.

    • getDistance

      public double getDistance(RealVector v) throws MathIllegalArgumentException
      Distance between two vectors.

      This method computes the distance consistent with the L2 norm, i.e. the square root of the sum of element differences, or Euclidean distance.

      Parameters:
      v - Vector to which distance is requested.
      Returns:
      the distance between two vectors.
      Throws:
      MathIllegalArgumentException - if v is not the same size as this vector.
      See Also:

    • getNorm

      public double getNorm()
      Returns the L2 norm of the vector.

      The L2 norm is the root of the sum of the squared elements.

      Returns:
      the norm.
      See Also:

    • getL1Norm

      public double getL1Norm()
      Returns the L1 norm of the vector.

      The L1 norm is the sum of the absolute values of the elements.

      Returns:
      the norm.
      See Also:

    • getLInfNorm

      public double getLInfNorm()
      Returns the L∞ norm of the vector.

      The L∞ norm is the max of the absolute values of the elements.

      Returns:
      the norm.
      See Also:

    • getL1Distance

      public double getL1Distance(RealVector v) throws MathIllegalArgumentException
      Distance between two vectors.

      This method computes the distance consistent with L1 norm, i.e. the sum of the absolute values of the elements differences.

      Parameters:
      v - Vector to which distance is requested.
      Returns:
      the distance between two vectors.
      Throws:
      MathIllegalArgumentException - if v is not the same size as this vector.

    • getLInfDistance

      public double getLInfDistance(RealVector v) throws MathIllegalArgumentException
      Distance between two vectors.

      This method computes the distance consistent with L∞ norm, i.e. the max of the absolute values of element differences.

      Parameters:
      v - Vector to which distance is requested.
      Returns:
      the distance between two vectors.
      Throws:
      MathIllegalArgumentException - if v is not the same size as this vector.
      See Also:

    • getMinIndex

      public int getMinIndex()
      Get the index of the minimum entry.
      Returns:
      the index of the minimum entry or -1 if vector length is 0 or all entries are NaN.

    • getMinValue

      public double getMinValue()
      Get the value of the minimum entry.
      Returns:
      the value of the minimum entry or NaN if all entries are NaN.

    • getMaxIndex

      public int getMaxIndex()
      Get the index of the maximum entry.
      Returns:
      the index of the maximum entry or -1 if vector length is 0 or all entries are NaN

    • getMaxValue

      public double getMaxValue()
      Get the value of the maximum entry.
      Returns:
      the value of the maximum entry or NaN if all entries are NaN.

    • mapMultiply

      public RealVector mapMultiply(double d)
      Multiply each entry by the argument. Returns a new vector. Does not change instance data.
      Parameters:
      d - Multiplication factor.
      Returns:
      this * d.

    • mapMultiplyToSelf

      public RealVector mapMultiplyToSelf(double d)
      Multiply each entry. The instance is changed in-place.
      Parameters:
      d - Multiplication factor.
      Returns:
      this.

    • mapSubtract

      public RealVector mapSubtract(double d)
      Subtract a value from each entry. Returns a new vector. Does not change instance data.
      Parameters:
      d - Value to be subtracted.
      Returns:
      this - d.

    • mapSubtractToSelf

      public RealVector mapSubtractToSelf(double d)
      Subtract a value from each entry. The instance is changed in-place.
      Parameters:
      d - Value to be subtracted.
      Returns:
      this.

    • mapDivide

      public RealVector mapDivide(double d)
      Divide each entry by the argument. Returns a new vector. Does not change instance data.
      Parameters:
      d - Value to divide by.
      Returns:
      this / d.

    • mapDivideToSelf

      public RealVector mapDivideToSelf(double d)
      Divide each entry by the argument. The instance is changed in-place.
      Parameters:
      d - Value to divide by.
      Returns:
      this.

    • outerProduct

      public RealMatrix outerProduct(RealVector v)
      Compute the outer product.
      Parameters:
      v - Vector with which outer product should be computed.
      Returns:
      the matrix outer product between this instance and v.

    • projection

      public RealVector projection(RealVector v) throws MathIllegalArgumentException, MathRuntimeException
      Find the orthogonal projection of this vector onto another vector.
      Parameters:
      v - vector onto which instance must be projected.
      Returns:
      projection of the instance onto v.
      Throws:
      MathIllegalArgumentException - if v is not the same size as this vector.
      MathRuntimeException - if this or v is the null vector

    • set

      public void set(double value)
      Set all elements to a single value.
      Parameters:
      value - Single value to set for all elements.

    • toArray

      public double[] toArray()
      Convert the vector to an array of doubles. The array is independent from this vector data: the elements are copied.
      Returns:
      an array containing a copy of the vector elements.

    • unitVector

      public RealVector unitVector() throws MathRuntimeException
      Creates a unit vector pointing in the direction of this vector. The instance is not changed by this method.
      Returns:
      a unit vector pointing in direction of this vector.
      Throws:
      MathRuntimeException - if the norm is zero.

    • unitize

      public void unitize() throws MathRuntimeException
      Converts this vector into a unit vector. The instance itself is changed by this method.
      Throws:
      MathRuntimeException - if the norm is zero.

    • sparseIterator

      public Iterator<RealVector.Entry> sparseIterator()
      Create a sparse iterator over the vector, which may omit some entries. The ommitted entries are either exact zeroes (for dense implementations) or are the entries which are not stored (for real sparse vectors). No guarantees are made about order of iteration.

      Note: derived classes are required to return an Iterator that returns non-null RealVector.Entry objects as long as Iterator.hasNext() returns true.

      Returns:
      a sparse iterator.

    • iterator

      public Iterator<RealVector.Entry> iterator()
      Generic dense iterator. Iteration is in increasing order of the vector index.

      Note: derived classes are required to return an Iterator that returns non-null RealVector.Entry objects as long as Iterator.hasNext() returns true.

      Returns:
      a dense iterator.

    • map

      public RealVector map(UnivariateFunction function)
      Acts as if implemented as: 
        return copy().mapToSelf(function);
      Returns a new vector. Does not change instance data.
      Parameters:
      function - Function to apply to each entry.
      Returns:
      a new vector.

    • mapToSelf

      public RealVector mapToSelf(UnivariateFunction function)
      Acts as if it is implemented as: 
        Entry e = null;
  for(Iterator<Entry> it = iterator(); it.hasNext(); e = it.next()) {
      e.setValue(function.value(e.getValue()));
  }
      Entries of this vector are modified in-place by this method.
      Parameters:
      function - Function to apply to each entry.
      Returns:
      a reference to this vector.

    • combine

      public RealVector combine(double a, double b, RealVector y) throws MathIllegalArgumentException
      Returns a new vector representing a * this + b * y, the linear combination of this and y. Returns a new vector. Does not change instance data.
      Parameters:
      a - Coefficient of this.
      b - Coefficient of y.
      y - Vector with which this is linearly combined.
      Returns:
      a vector containing a * this[i] + b * y[i] for all i.
      Throws:
      MathIllegalArgumentException - if y is not the same size as this vector.

    • combineToSelf

      public RealVector combineToSelf(double a, double b, RealVector y) throws MathIllegalArgumentException
      Updates this with the linear combination of this and y.
      Parameters:
      a - Weight of this.
      b - Weight of y.
      y - Vector with which this is linearly combined.
      Returns:
      this, with components equal to a * this[i] + b * y[i] for all i.
      Throws:
      MathIllegalArgumentException - if y is not the same size as this vector.

    • walkInDefaultOrder

      public double walkInDefaultOrder(RealVectorPreservingVisitor visitor)
      Visits (but does not alter) all entries of this vector in default order (increasing index).
      Parameters:
      visitor - the visitor to be used to process the entries of this vector
      Returns:
      the value returned by RealVectorPreservingVisitor.end() at the end of the walk

    • walkInDefaultOrder

      public double walkInDefaultOrder(RealVectorPreservingVisitor visitor, int start, int end) throws MathIllegalArgumentException
      Visits (but does not alter) some entries of this vector in default order (increasing index).
      Parameters:
      visitor - visitor to be used to process the entries of this vector
      start - the index of the first entry to be visited
      end - the index of the last entry to be visited (inclusive)
      Returns:
      the value returned by RealVectorPreservingVisitor.end() at the end of the walk
      Throws:
      MathIllegalArgumentException - if end < start.
      MathIllegalArgumentException - if the indices are not valid.

    • walkInOptimizedOrder

      public double walkInOptimizedOrder(RealVectorPreservingVisitor visitor)
      Visits (but does not alter) all entries of this vector in optimized order. The order in which the entries are visited is selected so as to lead to the most efficient implementation; it might depend on the concrete implementation of this abstract class.
      Parameters:
      visitor - the visitor to be used to process the entries of this vector
      Returns:
      the value returned by RealVectorPreservingVisitor.end() at the end of the walk

    • walkInOptimizedOrder

      public double walkInOptimizedOrder(RealVectorPreservingVisitor visitor, int start, int end) throws MathIllegalArgumentException
      Visits (but does not alter) some entries of this vector in optimized order. The order in which the entries are visited is selected so as to lead to the most efficient implementation; it might depend on the concrete implementation of this abstract class.
      Parameters:
      visitor - visitor to be used to process the entries of this vector
      start - the index of the first entry to be visited
      end - the index of the last entry to be visited (inclusive)
      Returns:
      the value returned by RealVectorPreservingVisitor.end() at the end of the walk
      Throws:
      MathIllegalArgumentException - if end < start.
      MathIllegalArgumentException - if the indices are not valid.

    • walkInDefaultOrder

      public double walkInDefaultOrder(RealVectorChangingVisitor visitor)
      Visits (and possibly alters) all entries of this vector in default order (increasing index).
      Parameters:
      visitor - the visitor to be used to process and modify the entries of this vector
      Returns:
      the value returned by RealVectorChangingVisitor.end() at the end of the walk

    • walkInDefaultOrder

      public double walkInDefaultOrder(RealVectorChangingVisitor visitor, int start, int end) throws MathIllegalArgumentException
      Visits (and possibly alters) some entries of this vector in default order (increasing index).
      Parameters:
      visitor - visitor to be used to process the entries of this vector
      start - the index of the first entry to be visited
      end - the index of the last entry to be visited (inclusive)
      Returns:
      the value returned by RealVectorChangingVisitor.end() at the end of the walk
      Throws:
      MathIllegalArgumentException - if end < start.
      MathIllegalArgumentException - if the indices are not valid.

    • walkInOptimizedOrder

      public double walkInOptimizedOrder(RealVectorChangingVisitor visitor)
      Visits (and possibly alters) all entries of this vector in optimized order. The order in which the entries are visited is selected so as to lead to the most efficient implementation; it might depend on the concrete implementation of this abstract class.
      Parameters:
      visitor - the visitor to be used to process the entries of this vector
      Returns:
      the value returned by RealVectorChangingVisitor.end() at the end of the walk

    • walkInOptimizedOrder

      public double walkInOptimizedOrder(RealVectorChangingVisitor visitor, int start, int end) throws MathIllegalArgumentException
      Visits (and possibly change) some entries of this vector in optimized order. The order in which the entries are visited is selected so as to lead to the most efficient implementation; it might depend on the concrete implementation of this abstract class.
      Parameters:
      visitor - visitor to be used to process the entries of this vector
      start - the index of the first entry to be visited
      end - the index of the last entry to be visited (inclusive)
      Returns:
      the value returned by RealVectorChangingVisitor.end() at the end of the walk
      Throws:
      MathIllegalArgumentException - if end < start.
      MathIllegalArgumentException - if the indices are not valid.

    • equals

      public boolean equals(Object other) throws MathRuntimeException

      Test for the equality of two real vectors. If all coordinates of two real vectors are exactly the same, and none are NaN, the two real vectors are considered to be equal. NaN coordinates are considered to affect globally the vector and be equals to each other - i.e, if either (or all) coordinates of the real vector are equal to NaN, the real vector is equal to a vector with all NaN coordinates.

      This method must be overriden by concrete subclasses of RealVector (the current implementation throws an exception).

      Overrides:
      equals in class Object
      Parameters:
      other - Object to test for equality.
      Returns:
      true if two vector objects are equal, false if other is null, not an instance of RealVector, or not equal to this RealVector instance.
      Throws:
      MathRuntimeException - if this method is not overridden.

    • hashCode

      public int hashCode() throws MathRuntimeException
      . This method must be overriden by concrete subclasses of RealVector (current implementation throws an exception).
      Overrides:
      hashCode in class Object
      Throws:
      MathRuntimeException - if this method is not overridden.

    • unmodifiableRealVector

      public static RealVector unmodifiableRealVector(RealVector v)
      Returns an unmodifiable view of the specified vector. The returned vector has read-only access. An attempt to modify it will result in a MathRuntimeException. However, the returned vector is not immutable, since any modification of v will also change the returned view. For example, in the following piece of code 
           RealVector v = new ArrayRealVector(2);
     RealVector w = RealVector.unmodifiableRealVector(v);
     v.setEntry(0, 1.2);
     v.setEntry(1, -3.4);
      the changes will be seen in the w view of v.
      Parameters:
      v - Vector for which an unmodifiable view is to be returned.
      Returns:
      an unmodifiable view of v.