带末端箭头装饰的 PGFlots 网格

Question

灵感来自这个问题我尝试用一​​个末端箭头来装饰我的 PGFPlots 网格。但是，这个末端箭头的位置不正确，导致线的末端显示在箭头尖端后面。这是一个最小的工作示例。大部分内容是从主要答案上述问题。

\documentclass{standalone}
\usepackage{tikz}
\usepackage{pgfplots}
\usepgfplotslibrary{colormaps}
\usetikzlibrary{decorations.markings}

\def\definemappedcolor#1{%
    %\message{Got #1^^J}%
    \pgfmathparse{#1*1000}% ... transform to range [0,1000]
    \pgfplotscolormapdefinemappedcolor{\pgfmathresult}%
}%

\tikzset{
  set arrow inside/.code={\pgfqkeys{/tikz/arrow inside}{#1}},
  set arrow inside={end/.initial=>, opt/.initial=},
  /pgf/decoration/Mark/.style={
    mark/.expanded=at position #1 with
    {
      \noexpand\definemappedcolor{#1}%
      \noexpand\arrow[\pgfkeysvalueof{/tikz/arrow inside/opt}]{\pgfkeysvalueof{/tikz/arrow inside/end}}
    }
  },
  arrow inside/.style 2 args={
    set arrow inside={#1},
    postaction={
      decorate,decoration={
        markings,Mark/.list={#2}
      }
    }
  },
}

\begin{document}

\begin{tikzpicture}
\begin{axis}[x=1cm, y=1cm, colormap/hot, point meta=explicit]
    \addplot[mesh] 
        coordinates {
        (0,0) [0]
        (1,1) [1]
        (2,2) [2]
        (3,3) [3]
        (4,2) [4]
    };

    \addplot[draw=none] 
        coordinates {
        (0,0) [0]
        (1,1) [1]
        (2,2) [2]
        (3,3) [3]
        (4,2) [4]
    } [arrow inside={end=stealth,opt={mapped color, scale=3}}{1}];
\end{axis}
\end{tikzpicture}

\end{document}

结果如下：

您可以清楚地看到，箭头尖端没有正确地连接到图的末尾，而是略微位于末尾之前。我尝试过使用shorten >=2pt，但似乎不起作用。

我怎样才能定位箭头，以便它“正确地”附着在情节线的末尾，即，我怎样才能防止看到情节线的末尾？

Answer 1

这里的问题是，您将箭头绘制在“之前绘制的内容”之上。这就是为什么没有“自动更正”此行为的原因，因为当您直接将箭头应用到线上时就会出现这种情况。

为了“模拟”该行为，您可以绘制一个双箭头。第一个箭头只是覆盖了“其他”线中不应看到的部分，第二个箭头是您想要添加的“真实”箭头。为此，您必须使用负分隔长度。

此外，我尝试寻找一种独立于所选线宽的解决方案，并且针对线宽达到“超厚”进行了测试。

有关更多详细信息，请查看代码中的注释。

\documentclass[border=5pt]{standalone}
\usepackage{pgfplots}
    \usetikzlibrary{
        % load this library to make use of the advanced arrow features
        arrows.meta,
        decorations.markings,
        pgfplots.colormaps,
    }

\def\definemappedcolor#1{%
    %\message{Got #1^^J}%
    \pgfmathparse{#1*1000}% ... transform to range [0,1000]
    \pgfplotscolormapdefinemappedcolor{\pgfmathresult}%
}%

\tikzset{
    set arrow inside/.code={\pgfqkeys{/tikz/arrow inside}{#1}},
    set arrow inside={end/.initial=>, opt/.initial=},
    /pgf/decoration/Mark/.style={
        mark/.expanded=at position #1 with {
            \noexpand\definemappedcolor{#1}%
            \noexpand\arrow[\pgfkeysvalueof{/tikz/arrow inside/opt}]{\pgfkeysvalueof{/tikz/arrow inside/end}}
        }
    },
    arrow inside/.style 2 args={
        set arrow inside={#1},
        postaction={
            decorate,decoration={
                markings,Mark/.list={#2}
            },
        },
    },
    % -------------------------------------------------------------------------
    my arrow/.tip={
        % this arrow tip shall overdraw the end of the "other" draw line
        Rectangle[
            % scale this arrow to 5 times the length of `line width'
            % (you can adjust this; it must only be longer than the "free" seen
            %  stuff of the "other" line)
            % and (only) being as width as `line width'
            length={0pt 5},
            width={0pt 1},
            % now adjust the `sep' to make it independent of line width
            sep={-3.05pt -5},
            % assume white background color
%            white,
            green,  % for debugging purposes only
        ]
        % and this is the arrow you actually want to plot
        Stealth[]
    },
    % -------------------------------------------------------------------------
}
\begin{document}
\begin{tikzpicture}
    \begin{axis}[
        x=1cm,
        y=1cm,
        colormap/hot,
        point meta=explicit,
    ]
        \addplot [
            mesh,
            % make (already) active to prove that I didn't move the line or arrow tip
            very thick,
        ] coordinates {
            (0,0) [0]
            (1,1) [1]
            (2,2) [2]
            (3,3) [3]
            (4,2) [4]
        };

        \addplot [
            draw=none,
            % make sure, this has the same `line width' as the previous plot
%            very thick,
        ]
            coordinates {
            (0,0) [0]
            (1,1) [1]
            (2,2) [2]
            (3,3) [3]
            (4,2) [4]
        % apply the defined arrow here
        } [arrow inside={end=my arrow}{1}];
    \end{axis}
\end{tikzpicture}
\end{document}