subMatrix method

Matrix subMatrix({ List<int>? rowIndices, List<int>? columnIndices, String rowRange = '', String colRange = '', int? rowStart, int? rowEnd, int? colStart, int? colEnd, })

Extracts a subMatrix from the given matrix using the specified row and column indices or ranges.

• rowIndices: Optional list of integers representing the row indices to include in the subMatrix.
• columnIndices: Optional list of integers representing the column indices to include in the subMatrix.
• rowRange: Optional string representing the row range (e.g. "1:3").
• colRange: Optional string representing the column range (e.g. "1:3").
• rowStart: Optional start index of the row range.
• rowEnd: Optional end index of the row range.
• colStart: Optional start index of the column range.
• colEnd: Optional end index of the column range.

Returns a new matrix containing the specified subMatrix.

Example:

var matrix = Matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]]);
var subMatrix = matrix.subMatrix(rowList: [0, 2], colList: [1, 2]);
print(subMatrix);
// Output:
// 2  3
// 8  9

Implementation

Matrix subMatrix(
    {List<int>? rowIndices,
    List<int>? columnIndices,
    String rowRange = '',
    String colRange = '',
    int? rowStart,
    int? rowEnd,
    int? colStart,
    int? colEnd}) {
  // If no row indices are provided, default to all rows
  // If rowStart or rowEnd is provided, use these to create the list
  final rowIndices_ = rowIndices ??
      (rowStart != null && rowEnd != null
          ? List.generate(rowEnd - rowStart + 1, (i) => rowStart + i)
          : (rowRange.isNotEmpty
              ? _Utils.parseRange(rowRange, rowCount)
              : (rowStart != null
                  ? List.generate(rowCount - rowStart, (i) => rowStart + i)
                  : (rowEnd != null
                      ? List.generate(rowEnd + 1, (i) => i)
                      : List.generate(rowCount, (i) => i)))));

  // If no column indices are provided, default to all columns
  // If colStart or colEnd is provided, use these to create the list
  final colIndices_ = columnIndices ??
      (colStart != null && colEnd != null
          ? List.generate(colEnd - colStart + 1, (i) => colStart + i)
          : (colRange.isNotEmpty
              ? _Utils.parseRange(colRange, columnCount)
              : (colStart != null
                  ? List.generate(columnCount - colStart, (i) => colStart + i)
                  : (colEnd != null
                      ? List.generate(colEnd + 1, (i) => i)
                      : List.generate(columnCount, (i) => i)))));

  if (rowIndices_.any((i) => i < 0 || i >= rowCount)) {
    throw Exception('Row indices are out of range');
  }

  if (colIndices_.any((i) => i < 0 || i >= columnCount)) {
    throw Exception('Column indices are out of range');
  }

  List<List<dynamic>> newData = rowIndices_.map((rowIndex) {
    return colIndices_.map((colIndex) => _data[rowIndex][colIndex]).toList();
  }).toList();

  return Matrix(newData);
}