java.lang.Object
dev.nm.algebra.linear.matrix.doubles.matrixtype.dense.diagonal.TridiagonalMatrix
All Implemented Interfaces:
Matrix, MatrixAccess, MatrixRing, MatrixTable, Densifiable, AbelianGroup<Matrix>, Monoid<Matrix>, Ring<Matrix>, Table, DeepCopyable

public class TridiagonalMatrix extends Object
A tri-diagonal matrix has non-zero entries only on the super, main and sub diagonals.
See Also:
  • Constructor Details

    • TridiagonalMatrix

      public TridiagonalMatrix(int dim)
      Constructs a 0 tri-diagonal matrix of dimension dim * dim.
      Parameters:
      dim - the dimension of the matrix
    • TridiagonalMatrix

      public TridiagonalMatrix(double[][] data)
      Constructs a tri-diagonal matrix from a 3-row 2D double[][] array such that:
      1. the first row is the super diagonal with (dim - 1) entries;
      2. the second row is the main diagonal with dim entries;
      3. the third row is the sub diagonal with (dim - 1) entries.
      For example,
      
               new double[][]{
                    {2, 5, 8, 11},
                    {1, 4, 7, 10, 13},
                    {3, 6, 9, 12}
                }
       
      gives \[ \begin{bmatrix} 1 invalid input: '&' 2 invalid input: '&' 0 invalid input: '&' 0 invalid input: '&' 0\\ 3 invalid input: '&' 4 invalid input: '&' 5 invalid input: '&' 0 invalid input: '&' 0\\ 0 invalid input: '&' 6 invalid input: '&' 7 invalid input: '&' 8 invalid input: '&' 0\\ 0 invalid input: '&' 0 invalid input: '&' 9 invalid input: '&' 10 invalid input: '&' 11\\ 0 invalid input: '&' 0 invalid input: '&' 0 invalid input: '&' 12 invalid input: '&' 13 \end{bmatrix} \] We allow null input when a diagonal is 0s. For example,
      
               new double[][]{
                    {2, 5, 8, 11},
                    {1, 4, 7, 10, 13},
                    null
                }
       
      gives \[ \begin{bmatrix} 1 invalid input: '&' 2 invalid input: '&' 0 invalid input: '&' 0 invalid input: '&' 0\\ 0 invalid input: '&' 4 invalid input: '&' 5 invalid input: '&' 0 invalid input: '&' 0\\ 0 invalid input: '&' 0 invalid input: '&' 7 invalid input: '&' 8 invalid input: '&' 0\\ 0 invalid input: '&' 0 invalid input: '&' 0 invalid input: '&' 10 invalid input: '&' 11\\ 0 invalid input: '&' 0 invalid input: '&' 0 invalid input: '&' 0 invalid input: '&' 13 \end{bmatrix} \] The following is not allowed because the dimension cannot be determined.
      
               new double[][]{
                    null,
                    null,
                    null
                }
       
      Parameters:
      data - the 2D array input
    • TridiagonalMatrix

      public TridiagonalMatrix(Matrix A)
      Casts a matrix to tridiagonal by copying the 3 diagonals (ignoring all other entries).
      Parameters:
      A - the matrix
    • TridiagonalMatrix

      public TridiagonalMatrix(TridiagonalMatrix that)
      Copy constructor performing a deep copy.
      Parameters:
      that - a tri-diagonal matrix
  • Method Details

    • deepCopy

      public TridiagonalMatrix deepCopy()
      Description copied from interface: DeepCopyable
      The implementation returns an instance created from this by the copy constructor of the class, or just this if the instance itself is immutable.
      Returns:
      an independent (deep) copy of the instance
    • add

      public Matrix add(Matrix that)
      Description copied from interface: MatrixRing
      this + that
      Specified by:
      add in interface AbelianGroup<Matrix>
      Specified by:
      add in interface MatrixRing
      Parameters:
      that - a matrix
      Returns:
      the sum of this and that
    • minus

      public Matrix minus(Matrix that)
      Description copied from interface: MatrixRing
      this - that
      Specified by:
      minus in interface AbelianGroup<Matrix>
      Specified by:
      minus in interface MatrixRing
      Parameters:
      that - a matrix
      Returns:
      the difference between this and that
    • scaled

      public TridiagonalMatrix scaled(double scalar)
      Description copied from interface: Matrix
      Scale this matrix, A, by a constant.
      Parameters:
      scalar - a double
      Returns:
      cA
    • opposite

      public TridiagonalMatrix opposite()
      Description copied from interface: MatrixRing
      Get the opposite of this matrix.
      Returns:
      -this
      See Also:
    • t

      public TridiagonalMatrix t()
      Description copied from interface: MatrixRing
      Get the transpose of this matrix. This is the involution on the matrix ring.
      Returns:
      the transpose of this matrix
    • ZERO

      public TridiagonalMatrix ZERO()
      Description copied from interface: MatrixRing
      Get a zero matrix that has the same dimension as this matrix.
      Returns:
      the 0 matrix
    • ONE

      public TridiagonalMatrix ONE()
      Description copied from interface: MatrixRing
      Get an identity matrix that has the same dimension as this matrix. For a non-square matrix, it zeros out the rows (columns) with index > nCols (nRows).
      Returns:
      an identity matrix
    • toDense

      public DenseMatrix toDense()
      Description copied from interface: Densifiable
      Densify a matrix, i.e., convert a matrix implementation to the standard dense matrix, DenseMatrix.
      Specified by:
      toDense in interface Densifiable
      Returns:
      a matrix representation in DenseMatrix
    • getDiagonal

      public DenseVector getDiagonal()
      Gets the main diagonal of the matrix.
      Returns:
      the main diagonal
    • getSuperDiagonal

      public DenseVector getSuperDiagonal()
      Gets the super-diagonal of the matrix.
      Returns:
      the super-diagonal
    • getSubDiagonal

      public DenseVector getSubDiagonal()
      Gets the sub-diagonal of the matrix.
      Returns:
      the sub-diagonal
    • nRows

      public int nRows()
      Description copied from interface: Table
      Gets the number of rows. Rows count from 1.
      Specified by:
      nRows in interface Table
      Returns:
      the number of rows
    • nCols

      public int nCols()
      Description copied from interface: Table
      Gets the number of columns. Columns count from 1.
      Specified by:
      nCols in interface Table
      Returns:
      the number of columns
    • set

      public void set(int i, int j, double value) throws MatrixAccessException
      Description copied from interface: MatrixAccess
      Set the matrix entry at [i,j] to a value. This is the only method that may change a matrix.
      Specified by:
      set in interface MatrixAccess
      Parameters:
      i - the row index
      j - the column index
      value - the value to set A[i,j] to
      Throws:
      MatrixAccessException - if i or j is out of range
    • get

      public double get(int i, int j) throws MatrixAccessException
      Description copied from interface: MatrixAccess
      Get the matrix entry at [i,j].
      Specified by:
      get in interface MatrixAccess
      Parameters:
      i - the row index
      j - the column index
      Returns:
      A[i,j]
      Throws:
      MatrixAccessException - if i or j is out of range
    • getRow

      public Vector getRow(int i)
      Description copied from interface: Matrix
      Get the specified row in the matrix as a vector.
      Specified by:
      getRow in interface Matrix
      Parameters:
      i - the row index
      Returns:
      the vector A[i, ]
    • getColumn

      public Vector getColumn(int j)
      Description copied from interface: Matrix
      Get the specified column in the matrix as a vector.
      Specified by:
      getColumn in interface Matrix
      Parameters:
      j - the column index
      Returns:
      a vector A[, j]
    • multiply

      public Matrix multiply(Matrix that)
      Description copied from interface: MatrixRing
      this * that
      Specified by:
      multiply in interface MatrixRing
      Specified by:
      multiply in interface Monoid<Matrix>
      Parameters:
      that - a matrix
      Returns:
      the product ofthis and that
    • multiply

      public Vector multiply(Vector v)
      Description copied from interface: Matrix
      Right multiply this matrix, A, by a vector.
      Specified by:
      multiply in interface Matrix
      Parameters:
      v - a vector
      Returns:
      Av, a vector
    • toString

      public String toString()
      Overrides:
      toString in class Object
    • equals

      public boolean equals(Object obj)
      Overrides:
      equals in class Object
    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object