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tag-icon • tag-icon tikz-pgf pgfplots
解释

因此，@Symbol1 的绝妙解决方案对于我的上一个问题，我有一个关于同一主题的新问题。使用建议的代码，更改的行为\pgfplotsplothandlerquiver@vis@path，point meta似乎不再起作用了……

mapped color这对和有影响\pgfplotspointmetatransformed

\documentclass[border=9,tikz]{standalone} 
\usepackage{pgfplots}\pgfplotsset{compat=newest}
\usetikzlibrary{arrows.meta}
\begin{document}

\makeatletter
\def\pgfplotsplothandlerquiver@vis@path#1{%
    % remember (x,y) in a robust way
    #1%
    \pgfmathsetmacro\pgfplots@quiver@x{\pgf@x}%
    \pgfmathsetmacro\pgfplots@quiver@y{\pgf@y}%
    % calculate (u,v) in relative coordinate
    \pgfplotsaxisvisphasetransformcoordinate\pgfplots@quiver@u\pgfplots@quiver@v\pgfplots@quiver@w%
    \pgfplotsqpointxy{\pgfplots@quiver@u}{\pgfplots@quiver@v}%
    \pgfmathsetmacro\pgfplots@quiver@u{\pgf@x-\pgfplots@quiver@x}%
    \pgfmathsetmacro\pgfplots@quiver@v{\pgf@y-\pgfplots@quiver@y}%
    % move to (x,y) and start drawing
    {%
        \pgftransformshift{\pgfpoint{\pgfplots@quiver@x}{\pgfplots@quiver@y}}%
        \pgfpathmoveto{\pgfpointorigin}%
        \pgfpathlineto{\pgfpoint\pgfplots@quiver@u\pgfplots@quiver@v}%
    }%
}%

  \begin{tikzpicture}
    \begin{axis}[axis equal]

      \addplot[
               point meta=x,
               quiver={u=x,v=y,
                 after arrow/.code={
                   \relax{% always protect the shift
                     \pgftransformshift{\pgfpoint{\pgfplots@quiver@x}{\pgfplots@quiver@y}}%
                     \node[below right]{\tiny\color{mapped color}\pgfplotspointmetatransformed};
                   }
                 }
               },
               ->,
               samples=10,domain=-1:1
              ] {x*x-1};


      \addplot[
               point meta=x,
               quiver={u=x,v=y,
                      every arrow/.append style={%
                        -{Latex[scale length={max(0.1,\pgfplotspointmetatransformed/1000)}]},mapped color
                      },
               },
               ->,
               samples=10,domain=-1:1
              ] {x*x};
   \end{axis}
  \end{tikzpicture}
\end{document}

对于未更改的版本，缩放和着色有效，但对于更改的版本，这两项功能均无效。

在此处输入图片描述

为了完整起见，pgfplots替换了原始代码（我在这里看不到有关元值的任何内容？！？）

\def\pgfplotsplothandlerquiver@vis@path#1{%
    \pgfpathmoveto{#1}%
    \pgfplotsaxisvisphasetransformcoordinate\pgfplots@quiver@u\pgfplots@quiver@v\pgfplots@quiver@w
    \pgfpathlineto{%
        \pgfplotsifcurplotthreedim{%
            \pgfplotsqpointxyz\pgfplots@quiver@u\pgfplots@quiver@v\pgfplots@quiver@w
        }{%
            \pgfplotsqpointxy\pgfplots@quiver@u\pgfplots@quiver@v
        }%
    }%
}%

答案1

以下对我有用。

\documentclass[border=9,tikz]{standalone} 
\usepackage{pgfplots}\pgfplotsset{compat=newest}
\usetikzlibrary{arrows.meta}
\begin{document}

\makeatletter
\def\pgfplotsplothandlerquiver@vis@path#1{%
    % remember (x,y) in a robust way
    #1%
    \pgfmathsetmacro\pgfplots@quiver@x{\pgf@x}\global\let\pgfplots@quiver@x\pgfplots@quiver@x%
    \pgfmathsetmacro\pgfplots@quiver@y{\pgf@y}\global\let\pgfplots@quiver@y\pgfplots@quiver@y%
    % calculate (u,v) in relative coordinate
    \pgfplotsaxisvisphasetransformcoordinate\pgfplots@quiver@u\pgfplots@quiver@v\pgfplots@quiver@w%
    \pgfplotsqpointxy{\pgfplots@quiver@u}{\pgfplots@quiver@v}%
    \pgfmathsetmacro\pgfplots@quiver@u{\pgf@x-\pgfplots@quiver@x}%
    \pgfmathsetmacro\pgfplots@quiver@v{\pgf@y-\pgfplots@quiver@y}%
    % move to (x,y) and start drawing
    {%
        \pgftransformshift{\pgfpoint{\pgfplots@quiver@x}{\pgfplots@quiver@y}}%
        \pgfpathmoveto{\pgfpointorigin}%
        \pgfpathlineto{\pgfpoint\pgfplots@quiver@u\pgfplots@quiver@v}%
    }%
}%

    \begin{tikzpicture}
        \begin{axis}[axis equal]
            \addplot[
                point meta=x,
                quiver={
                    u=x,v=y,
                    every arrow/.append style={%
                        -{Latex[scale length={max(0.1,\pgfplotspointmetatransformed/1000)}]},mapped color
                    },
                    after arrow/.code={
                        \relax{% always protect the shift
                            \pgftransformshift{\pgfpoint{\pgfplots@quiver@x}{\pgfplots@quiver@y}}%
                            \node[below right]{\tiny\color{mapped color}\pgfplotspointmetatransformed};
                        }
                    }
                },
                ->,samples=10,domain=-1:1
            ]{x*x-1};
            \addplot[
                point meta=x,
                quiver={
                    u=x,v=y,
                    every arrow/.append style={%
                        -{Latex[scale length={max(0.1,\pgfplotspointmetatransformed/1000)}]},mapped color
                    },
                },
                ->,samples=10,domain=-1:1
            ]{x*x};
        \end{axis}
    \end{tikzpicture}
\end{document}

解释

此代码与您上一个问题中的代码的主要区别在于

\pgfmathsetmacro\pgfplots@quiver@x{\pgf@x}
\pgfmathsetmacro\pgfplots@quiver@y{\pgf@y}

制成

\pgfmathsetmacro\pgfplots@quiver@x{\pgf@x}\global\let\pgfplots@quiver@x\pgfplots@quiver@x%
\pgfmathsetmacro\pgfplots@quiver@y{\pgf@y}\global\let\pgfplots@quiver@y\pgfplots@quiver@y%

这表明错误是由额外分组引起的。但为什么会有额外的分组？因为当 pgfplots 遇到

\draw[/pgfplots/quiver/every arrow]...

的选项\draw按照惯例只影响这个\draw。因此 Ti钾Z 会将其放入\draw一个组中。由于\pgfplotsplothandlerquiver@vis@path被放入一个组中，所以您无法\pgfplots@quiver@x从外部看到（特别是在 中after arrow）。

顺便说一下，#1的\pgfplotsplothandlerquiver@vis@path大致意思是，

\global\pgf@x=\pgf@x
\global\pgf@x=\pgf@y

并且上面的分析也证明了这种做法的必要性。

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