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如何从交点绘制到 x 轴？

tag-icon • tag-icon tikz-pgf pgfplots
如何从交点绘制到 x 轴？

基于如何在 pgfplot 中绘制直到与绘图线相交？我想出了这个：

\documentclass{memoir}
\usepackage{tikz}
\usepackage{pgfplots}
\usetikzlibrary{intersections, calc}

\begin{document}
\begin{figure}
\begin{tikzpicture}
\begin{axis}[ymin=0,ymax=100,xmin=5E-13,xmax=3E-4,
xlabel=Concentration,
ylabel=Effect (\%),
axis lines=left,
width=2\marginparwidth,
height=1.4\marginparwidth,
ytick={0,25,50,75,100},
xmode = log,
tick label style = {font=\footnotesize},
]
\addplot [color=black, name path=P] coordinates {
    (1E-4, 0)
    (1E-5, 0)
    (1E-6, 2)
    (1E-7, 21)
    (1E-8, 66)
    (1E-9, 88)
    (1E-10, 94)
    (1E-11, 95)
    (1E-12, 96)
    };
\addplot [only marks] coordinates {
    (1E-4, 0)
    (1E-5, 0)
    (1E-6, 2)
    (1E-7, 21)
    (1E-8, 66)
    (1E-9, 88)
    (1E-10, 94)
    (1E-11, 95)
    (1E-12, 96)
    };

\path [name path=A] (axis cs:1E-12, 50) -- (axis cs:1E-4, 50);
\path [name intersections={of=A and P}];
\draw[->, thick] (axis cs:1E-12, 50) -- (intersection-1); 
\path [name path=B] (axis cs:1E-12, 0) -- (axis cs:1E-4, 0);
\draw[->, thick] (intersection-1) -| B);
    \end{axis}

\end{tikzpicture}
\end{figure}
\end{document}

但是，我想从最后一个箭头的末端向下绘制另一个箭头，直到 x 轴。我以为这很容易，但似乎并非如此。显然，我无法像-|我尝试的那样在事物之间画一条线。我该怎么办？

答案1

垂直坐标系的工作；你可以这样说

\draw[->, thick,red] (intersection-1) -- ({intersection-1}|-{axis cs:0,0});

在此处输入图片描述

完整示例：

\documentclass{memoir}
\usepackage{tikz}
\usepackage{pgfplots}
\usetikzlibrary{intersections, calc}

\begin{document}

\begin{figure}
\begin{tikzpicture}
\begin{axis}[ymin=0,ymax=100,xmin=5E-13,xmax=3E-4,
xlabel=Concentration,
ylabel=Effect (\%),
axis lines=left,
width=2\marginparwidth,
height=1.4\marginparwidth,
ytick={0,25,50,75,100},
xmode = log,
tick label style = {font=\footnotesize},
]
\addplot [color=black, name path=P] coordinates {
    (1E-4, 0)
    (1E-5, 0)
    (1E-6, 2)
    (1E-7, 21)
    (1E-8, 66)
    (1E-9, 88)
    (1E-10, 94)
    (1E-11, 95)
    (1E-12, 96)
    };
\addplot [only marks] coordinates {
    (1E-4, 0)
    (1E-5, 0)
    (1E-6, 2)
    (1E-7, 21)
    (1E-8, 66)
    (1E-9, 88)
    (1E-10, 94)
    (1E-11, 95)
    (1E-12, 96)
    };
\path [name path=A] (axis cs:1E-12, 50) -- (axis cs:1E-4, 50);
\path [name intersections={of=A and P}];
\draw[->, thick] (axis cs:1E-12, 50) -- (intersection-1); 
\draw[->, thick,red] 
(intersection-1) -- ({intersection-1}|-{axis cs:0,0}); 
\end{axis}
\end{tikzpicture}
\end{figure}

\end{document}

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