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无法使用 tikz 显示该函数

tag-icon • tag-icon tikz-pgf ktikz
无法使用 tikz 显示该函数

你好，我正在尝试绘制以下 tikz 代码：

\def\tr{0.1}
\def\ts{0.6}
\def\al{1.3}
\def\n{1.6}
\def\I{0.3506}
\def\ti{0.4071}
\def\S{-0.1340}
\def\Sangle{-42}
\def\f1{0.8}

\begin{tikzpicture}[domain=-3:5, xscale=1, yscale=5, >=latex]
  \draw[very thin,color=gray!30] (-3,0)
    grid[xstep=0.5, ystep=0.1] (5,0.7);
  \draw[->, line width=1pt] (-3,0) -- (5.25,0)
    node[below] {$\log(\psi)$};
  \draw[->, line width=1pt] (-3,0) -- (-3,0.75)
    node[left] {$U(\psi)$};
  \draw[color=green!30!black, thick, smooth]
    plot[id=x, domain=-3:5]
    function{\tr+(\ts-\tr)/(1+(\al*exp(x))**\n)**(1-1/\n)};
  \node[left] (tr) at (-3,\tr) {$U_r$};
  \node[left] (ts) at (-3,\ts) {$U_s$};
  \draw[dashed] (\I,0) node[below] {$I$} -- (\I,\ti) -- (-3,\ti)
    node[left] {$U_i$};
  \draw[color=green!30!black, dashed]
    plot[id=x, domain=-1.5:3]
    function{\ti+\S*(x-\I)};
  \draw[|<->|] (\I,\ti)++(1,0) arc (0:\Sangle:0.8 and 0.15);
  \path (\I,\ti)++(0.5*1.5\Sangle/8:1)
    node[right=-1pt] {$\tan^{-1}(S)$};
  \node[anchor=base] (vg) at (1,0.8)
    {$U(\psi) = U_r+\displaystyle\frac{U_s-U_r}{(1+(\alpha\psi)^n)^m}$};
\end{tikzpicture}

但由于某种原因，该函数没有绘制出来，我只得到这个：

enter image description here

有人能告诉我我做错了什么吗？

答案1

是的，很可能你没有安装相关软件（gnuplot？）。但你不需要它，你可以用 Ti 绘制函数钾仅限 Z。

\documentclass[tikz]{standalone}
\def\TR{0.1}
\def\TS{0.6}
\def\al{1.3}
\def\n{1.6}
\def\I{0.3506}
\def\ti{0.4071}
\def\S{-0.1340}
\def\Sangle{-42}
\def\fone{0.8}
\begin{document}
\begin{tikzpicture}[xscale=1, yscale=5, >=latex]
  \draw[very thin,color=gray!30] (-3,0)
    grid[xstep=0.5, ystep=0.1] (5,0.7);
  \draw[->, line width=1pt] (-3,0) -- (5.25,0)
    node[below] {$\log(\psi)$};
  \draw[->, line width=1pt] (-3,0) -- (-3,0.75)
    node[left] {$U(\psi)$};
  \draw[color=green!30!black, thick, smooth]
    plot[id=x, domain=-3:5]
    ({\x},{\TR+(\TS-\TR)/(1+(\al*exp(\x))^\n)^(1-1/\n)});
  \node[left] (tr) at (-3,\TR) {$U_r$};
  \node[left] (ts) at (-3,\TS) {$U_s$};
  \draw[dashed] (\I,0) node[below] {$I$} -- (\I,\ti) -- (-3,\ti)
    node[left] {$U_i$};
  \draw[color=green!30!black, dashed]
    plot[id=x, domain=-1.5:3]
    ({\x},{\ti+\S*(\x-\I)});
  \draw[|<->|] (\I,\ti)++(1,0) arc (0:\Sangle:0.8 and 0.15);
  \path (\I,\ti)++(0.5*1.5\Sangle/8:1)
    node[right=-1pt] {$\tan^{-1}(S)$};
  \node[anchor=base] (vg) at (1,0.8)
    {$U(\psi) = U_r+\displaystyle\frac{U_s-U_r}{(1+(\alpha\psi)^n)^m}$};
\end{tikzpicture}
\end{document}
\endinput

enter image description here

请注意，我利用这个机会为一些变量赋予了更安全的名称，例如，\tr因为它代表跟踪，所以非常危险，等等。还请注意，这def\f1{0.8}可能不是你想要的，LaTeX 不接受宏名称中的数字。

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