Tikz：在图例中添加额外信息

Question

我想在图例中添加额外的信息。我在 MWE 中完成了此操作，我创建了一个虚拟图以便在图例中添加额外的信息。如何在不创建假 \addplot 的情况下完成此操作？谢谢。

\documentclass[letterpaper]{article}
\usepackage{tikz,pgfplots}



\begin{document}

\begin{tikzpicture}
    \begin{axis}[
        ymax = 3000,
        ymin = -3000,
        height=9cm,
        width=9cm,
        grid=major,
    ]

    \addplot {-x^5 - 242};
    \addlegendentry{model}

    \addplot coordinates {
        (-4.77778,2027.60977)
        (-3.55556,347.84069)
        (-2.33333,22.58953)
        (-1.11111,-493.50066)
        (0.11111,46.66082)
        (1.33333,-205.56286)
        (2.55556,-341.40638)
        (3.77778,-1169.24780)
        (5.00000,-3269.56775)
    };
    \addlegendentry{estimate}

    \addplot[only marks,white] coordinates {(-1,-15000)}; % dummy plot to add extra legend entry.....
    \addlegendentry{Additional Information}

    \end{axis}
\end{tikzpicture}
\end{document} 

Answer 1

神奇的命令行是

\addlegendimage{empty legend}

我也建议添加\pgfplotsset{compat=1.16}，但这里不需要。

\documentclass[letterpaper]{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}% <-added but not necessary
\begin{document}

\begin{tikzpicture}
    \begin{axis}[
        ymax = 3000,
        ymin = -3000,
        height=9cm,
        width=9cm,
        grid=major,
    ]

    \addplot {-x^5 - 242};
    \addlegendentry{model}

    \addplot coordinates {
        (-4.77778,2027.60977)
        (-3.55556,347.84069)
        (-2.33333,22.58953)
        (-1.11111,-493.50066)
        (0.11111,46.66082)
        (1.33333,-205.56286)
        (2.55556,-341.40638)
        (3.77778,-1169.24780)
        (5.00000,-3269.56775)
    };
    \addlegendentry{estimate}

    \addlegendimage{empty legend}
    \addlegendentry{Additional Information}

    \end{axis}
\end{tikzpicture}
\end{document}