Package jline.util.matrix

Class ColumnView

  • All Implemented Interfaces:
    
public class ColumnView

    A lightweight view into a column of a sparse matrix that doesn't copy data. This provides efficient access to matrix column elements without the overhead of creating a new Matrix object and copying all the data.

    This is particularly useful for large sparse matrices where you need to access column elements frequently, such as in iterative algorithms.

    Example usage:

    Matrix bigMatrix = ...; // 1M x 1000 sparse matrix
ColumnView col = bigMatrix.getColumnView(5);

// Efficient access - only processes non-zero elements
for (int i = 0; i < col.getNonZeroCount(); i++) {
    int row = col.getNonZeroRow(i);
    double value = col.getNonZeroValue(i);
    // process (row, value) pair
}

// Or get any element (returns 0.0 for non-stored elements)
double val = col.get(100);
    Since:

    1.0

    Author:

    QORE Lab, Imperial College London

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description

    • Field Summary

      Fields 
      Modifier and Type Field Description
      public final int columnIndex
      public final int numRows

    • Constructor Summary

      Constructors 
      Constructor Description

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description

    • Method Summary

      Modifier and Type Method Description
      int getColumnIndex() Returns the column index that this view represents.
      int getNumRows() Returns the total number of rows in the column (including zeros).
      double get(int row) Returns the value at the specified row in this column.
      int getNonZeroCount() Returns the number of non-zero elements in this column.
      int getNonZeroRow(int i) Returns the row index of the i-th non-zero element in this column.
      double getNonZeroValue(int i) Returns the value of the i-th non-zero element in this column.
      boolean hasNonZeros() Checks if this column has any non-zero elements.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

    • Method Detail

      • getColumnIndex

         int getColumnIndex()

        Returns the column index that this view represents.

        Returns:

        the column index

      • getNumRows

         int getNumRows()

        Returns the total number of rows in the column (including zeros).

        Returns:

        the number of rows

      • get

         double get(int row)

        Returns the value at the specified row in this column. This method searches through the non-zero elements, so it's O(nnz_in_column). For frequent access to multiple elements, consider using the non-zero iterators.

        Parameters:
        row - the row index
        Returns:

        the value at (row, column), or 0.0 if not stored

      • getNonZeroCount

         int getNonZeroCount()

        Returns the number of non-zero elements in this column.

        Returns:

        the count of non-zero elements

      • getNonZeroRow

         int getNonZeroRow(int i)

        Returns the row index of the i-th non-zero element in this column.

        Parameters:
        i - the index into the non-zero elements (0 to getNonZeroCount()-1)
        Returns:

        the row index

      • getNonZeroValue

         double getNonZeroValue(int i)

        Returns the value of the i-th non-zero element in this column.

        Parameters:
        i - the index into the non-zero elements (0 to getNonZeroCount()-1)
        Returns:

        the value

      • hasNonZeros

         boolean hasNonZeros()

        Checks if this column has any non-zero elements.

        Returns:

        true if the column contains at least one non-zero element