code: public SparseDoubleVector getColumnVector(int column) {
          SparseDoubleVector values = new SparseHashDoubleVector(rows);
          for (int row = 0; row < rows; ++row) {
              double d = get(row, column);
              if (d != 0)
                  values.set(row, d);
          }
          return values;
      }
docs: Returns a {@link DoubleVector} of the contents of the column.
  
  @param column {@inheritDoc}
  @return {@inheritDoc}