java.lang.Object
dev.nm.algebra.linear.matrix.doubles.operation.SubMatrixRef
All Implemented Interfaces:
Matrix, MatrixAccess, MatrixRing, MatrixTable, AbelianGroup<Matrix>, Monoid<Matrix>, Ring<Matrix>, Table, DeepCopyable

public class SubMatrixRef extends Object implements Matrix
This is a 'reference' to a sub-matrix of a larger matrix without copying it. For performance reason, we often want to work with a sub-matrix without copying it.

The reference sub-matrix is immutable.

  • Constructor Details

    • SubMatrixRef

      public SubMatrixRef(Matrix A, int[] rows, int[] cols)
      Constructs a sub-matrix reference.
      Parameters:
      A - a matrix
      rows - the row indices
      cols - the column indices
      Throws:
      IndexOutOfBoundsException - if rowFrom, rowTo, colFrom, or colTo is invalid
    • SubMatrixRef

      public SubMatrixRef(Matrix A, int rowFrom, int rowTo, int colFrom, int colTo)
      Constructs a sub-matrix reference.
      Parameters:
      A - a matrix
      rowFrom - the beginning row index
      rowTo - the ending row index
      colFrom - the beginning column index
      colTo - the ending column index
    • SubMatrixRef

      public SubMatrixRef(Matrix A)
      Constructs a reference to the whole matrix.
      Parameters:
      A - a matrix
  • Method Details

    • 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
    • get

      public double get(int i, int j)
      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]
    • 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]
    • 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
    • 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
    • scaled

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

      public Matrix opposite()
      Description copied from interface: MatrixRing
      Get the opposite of this matrix.
      Specified by:
      opposite in interface AbelianGroup<Matrix>
      Specified by:
      opposite in interface MatrixRing
      Returns:
      -this
      See Also:
    • ZERO

      public Matrix ZERO()
      Description copied from interface: MatrixRing
      Get a zero matrix that has the same dimension as this matrix.
      Specified by:
      ZERO in interface AbelianGroup<Matrix>
      Specified by:
      ZERO in interface MatrixRing
      Returns:
      the 0 matrix
    • ONE

      public Matrix 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).
      Specified by:
      ONE in interface MatrixRing
      Specified by:
      ONE in interface Monoid<Matrix>
      Returns:
      an identity matrix
    • toString

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

      public Matrix t()
      Description copied from interface: MatrixRing
      Get the transpose of this matrix. This is the involution on the matrix ring.
      Specified by:
      t in interface MatrixRing
      Returns:
      the transpose of this matrix
    • deepCopy

      public SubMatrixRef deepCopy()
      Returns this as the reference is immutable.
      Specified by:
      deepCopy in interface DeepCopyable
      Specified by:
      deepCopy in interface Matrix
      Returns:
      this
    • set

      @Deprecated public void set(int i, int j, double value) throws MatrixAccessException
      Deprecated.
      SubMatrixRef is immutable
      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