NaN   NaN  NaN   NaN

        Keep all original rows and columns and also all original values

        >>> df.compare(df2, keep_shape=True, keep_equal=True)
          col1       col2       col3
          self other self other self other
        0    a     c  1.0   1.0  1.0   1.0
        1    a     a  2.0   2.0  2.0   2.0
        2    b     b  3.0   3.0  3.0   4.0
        3    b     b  NaN   NaN  4.0   4.0
        4    a     a  5.0   5.0  5.0   5.0
        rˆ