code: public static void addColTimes(DenseDoubleMatrix2D matrix, long diag, long fromRow, long col,
  			double factor) {
  		long rows = matrix.getRowCount();
  		for (long row = fromRow; row < rows; row++) {
  			matrix.setDouble(matrix.getDouble(row, col) - factor * matrix.getDouble(row, diag),
  					row, col);
  		}
  	}
docs: Add a factor times one column to another column
  
  @param matrix
  the matrix to modify
  @param diag
  coordinate on the diagonal
  @param fromRow
  first row to process
  @param col
  column to process
  @param factor
  factor to multiply