未明确设置时轴限制的键名称

Question

xmin在下面的最小工作示例中，我使用、xmax和键ymin来ymax计算注释的坐标。但是，这仅在轴选项中明确设置轴限值时才有效。

当我没有明确设置轴限值时，我也希望代码能够正常工作。在这种情况下，轴限值存储在哪些键名中？

最小工作示例：

% Mind section '4.17 Custom annotations' of the PGFplots manual Revision 1.12 (2015/01/31).
\documentclass[margin=1cm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usetikzlibrary{calc}

\newcommand{\slopeTriangle}[9]
{
    % Calculate auxilliary quantities.
    \pgfmathsetmacro{\xA}{#6+(#1+#2)*(#7-#6)}
    \pgfmathsetmacro{\yA}{#8+#3*(#9-#8)}
    \pgfmathsetmacro{\xB}{#6+#1*(#7-#6)}
    \pgfmathsetmacro{\yB}{\yA}
    \pgfmathsetmacro{\xC}{\xA}
    \pgfmathsetmacro{\yC}{\yA+(\xA-\xB)*#4}

    % Define coordinates for \draw.
    \coordinate (A) at (axis cs:\xA,\yA);
    \coordinate (B) at (axis cs:\xB,\yB);
    \coordinate (C) at (axis cs:\xC,\yC);

    % Draw slope triangle.
    \draw[#5] (A)--(B) node[pos=0.5,anchor=north] {1};
    \draw[#5] (B)--(C);
    \draw[#5] (C)--(A) node[pos=0.5,anchor=west] {1};
}

\begin{document}
    \begin{tikzpicture}
        \begin{axis}
        [
            xtick={-0.1,0,1,1.1},
            xmin=-0.1, % WHAT IF I REMOVE THIS?
            xmax=1.1, % WHAT IF I REMOVE THIS?
            xlabel=$x$,
            ytick={-0.2,0,2,2.2},
            ymin=-0.2, % WHAT IF I REMOVE THIS?
            ymax=2.2, % WHAT IF I REMOVE THIS?
            ylabel style={rotate=-90},
            ylabel=$y$,
            unit vector ratio=2 1 1,
            clip=false
        ]
            \addplot[blue,domain=0:1] {x};
            \addplot[red,domain=0:1] {2*x};

            \pgfkeysgetvalue{/pgfplots/xmin}{\xmin} % IF THE xmin IS NOT SET EXPLICITLY, THEN WHAT IS THE KEYNAME?
            \pgfkeysgetvalue{/pgfplots/xmax}{\xmax} % IF THE xmax IS NOT SET EXPLICITLY, THEN WHAT IS THE KEYNAME?
            \pgfkeysgetvalue{/pgfplots/ymin}{\ymin} % IF THE ymin IS NOT SET EXPLICITLY, THEN WHAT IS THE KEYNAME?
            \pgfkeysgetvalue{/pgfplots/ymax}{\ymax} % IF THE ymax IS NOT SET EXPLICITLY, THEN WHAT IS THE KEYNAME?

            \slopeTriangle{0.8}{0.1}{0.1}{1}{blue}{\xmin}{\xmax}{\ymin}{\ymax};
        \end{axis}
    \end{tikzpicture}
\end{document}

Answer 1

根据pgfplots的参考文献/pgfplots/xmin，它成立

在可视化阶段，即在 \end{axis} 期间，这些键将设置为最终轴限值。您可以通过以下方式访问这些值\pgfkeysvalueof{/pgfplots/xmin}

因此，您只需将您的计算和节点生成括起来\pgfplotsextra，您的代码就会收到预期的（自动计算的）值。我添加了一个合适的标题来显示这些值（用于调试目的）：

\documentclass[margin=1cm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usetikzlibrary{calc}

\newcommand{\slopeTriangle}[9]
{
    % Calculate auxilliary quantities.
    \pgfmathsetmacro{\xA}{#6+(#1+#2)*(#7-#6)}
    \pgfmathsetmacro{\yA}{#8+#3*(#9-#8)}
    \pgfmathsetmacro{\xB}{#6+#1*(#7-#6)}
    \pgfmathsetmacro{\yB}{\yA}
    \pgfmathsetmacro{\xC}{\xA}
    \pgfmathsetmacro{\yC}{\yA+(\xA-\xB)*#4}

    % Define coordinates for \draw.
    \coordinate (A) at (axis cs:\xA,\yA);
    \coordinate (B) at (axis cs:\xB,\yB);
    \coordinate (C) at (axis cs:\xC,\yC);

    % Draw slope triangle.
    \draw[#5] (A)--(B) node[pos=0.5,anchor=north] {1};
    \draw[#5] (B)--(C);
    \draw[#5] (C)--(A) node[pos=0.5,anchor=west] {1};
}

\begin{document}
    \begin{tikzpicture}
        \begin{axis}
        [
            xtick={-0.1,0,1,1.1},
            %xmin=-0.1, % WHAT IF I REMOVE THIS?
            %xmax=1.1, % WHAT IF I REMOVE THIS?
            xlabel=$x$,
            ytick={-0.2,0,2,2.2},
            %ymin=-0.2, % WHAT IF I REMOVE THIS?
            %ymax=2.2, % WHAT IF I REMOVE THIS?
            ylabel style={rotate=-90},
            ylabel=$y$,
            unit vector ratio=2 1 1,
            clip=false,
            % Show (automatically) computed limits:
            title={%
                 Axis limits are
                 $
                [\pgfmathprintnumber{\pgfkeysvalueof{/pgfplots/xmin}}
                :\pgfmathprintnumber{\pgfkeysvalueof{/pgfplots/xmax}}
                ] \times
                [\pgfmathprintnumber{\pgfkeysvalueof{/pgfplots/ymin}}
                :\pgfmathprintnumber{\pgfkeysvalueof{/pgfplots/ymax}}
                ]$
            },
        ]
            \addplot[blue,domain=0:1] {x};
            \addplot[red,domain=0:1] {2*x};

            \pgfplotsextra{
            \pgfkeysgetvalue{/pgfplots/xmin}{\xmin}
            \pgfkeysgetvalue{/pgfplots/xmax}{\xmax}
            \pgfkeysgetvalue{/pgfplots/ymin}{\ymin}
            \pgfkeysgetvalue{/pgfplots/ymax}{\ymax}
            \slopeTriangle{0.8}{0.1}{0.1}{1}{blue}{\xmin}{\xmax}{\ymin}{\ymax};
            }
        \end{axis}
    \end{tikzpicture}
\end{document}