将箭头添加到绘图中

Question 1

您可以marking使用\usetikzlibrary{decorations.markings}

xticklabels={}/ yticklabels={}：删除 x,y 刻度标签
axis x line=middle/axis y line=middle或者只是axis lines=middle：轴线经过原点
every axis y label/.style={ at={...：位置轴标签
postaction={decorate, decoration={markings, mark=at position 0.105 with {\arrow{<};},或... mark=between positions 0.16 and 0.4 step 0.2 with：将箭头添加到图中

您也可以使用箭头尖，latex只需使用\arrow{latex}。语法-latex意味着将类型的箭头放在latex路径末尾-，因此-这里不需要。箭头名称只是latex。所以你只需要箭头名称 => \arrow{latex}。（参考 Gonzalo Medina）。

如果希望箭头方向相反，可以这样旋转：

\arrow[rotate=-180]{latex};

或使用箭头latex reversed。

\arrow{latex reversed};

使用其他箭头或旋转箭头样式时，由于箭头大小不同，您可能需要稍微修改定位。使用反复试验来找到您的位置。其不是最佳的，总是有更好的steps（见：位置之间）。我的策略是注意总尺寸并对齐例如前两个箭头，然后您可以添加 +0.2*x... 这里的维度：2.5pi -> 零交叉或最小/最大值 0.2、0.4、0.6、0.8，如果我的建议让您感到困惑，您必须找到自己的方法。：

 mark=at position 0.08 with {\arrow[red,rotate=-180]{latex};},% or latex reversed
 mark=at position 0.28 with {\arrow[red,rotate=-180]{latex};},
 mark=at position 0.52 with {\arrow[blue,rotate=0]{latex};},%0.48 = same direction
 mark=at position 0.72 with {\arrow[blue,rotate=0]{latex};},%0.68 = same direction
 mark=at position 0.88 with {\arrow[blue,rotate=-180]{latex};}

像这样？

或带有\arrow{latex}和修改后的定位。

梅威瑟：

\documentclass{standalone}
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\usetikzlibrary{decorations.markings}

\begin{document}
\begin{tikzpicture}
\begin{axis}[scale=0.9, xmin=-3, xmax=10, ymin=-3, ymax=3, grid = both,
axis x line=middle,thick,xticklabels={},
axis y line=middle,tick style={draw=none},yticklabels={},
xlabel=$y$, ylabel=$\frac{dy}{dt}$,
every axis y label/.style={
    at={(ticklabel* cs:1.00)},
    anchor=west,
},
every axis x label/.style={
    at={(ticklabel* cs:1.00)},
    anchor=west,
}
%,every axis y label/.style={at={(current axis.north west)},xshift=+10pt,rotate=0},
]
%\addplot[red, ultra thick] expression[domain=0:20, samples=100]{1.2*x*(1-(x/15))-(4*x)/(0.5+x)};
\addplot[domain=0:2.5*pi,samples=100,blue,
postaction={decorate, decoration={markings,
%        mark=between positions 0.16 and 0.4 step 0.2 with {\arrow{<};},
%        mark=between positions 0.67 and 0.9 step 0.2 with {\arrow{>};}
mark=at position 0.105 with {\arrow{<};},
mark=at position 0.31 with {\arrow{<};},
mark=at position 0.51 with {\arrow{>};},
mark=at position 0.71 with {\arrow{>};},
 mark=at position 0.9 with {\arrow{<};}
%% Version 2:
 %%mark=at position 0.08 with {\arrow[red,rotate=-180]{latex};},% or latex reversed
 %%mark=at position 0.28 with {\arrow[red,rotate=-180]{latex};},
 %%mark=at position 0.52 with {\arrow[blue,rotate=0]{latex};},
 %%mark=at position 0.72 with {\arrow[blue,rotate=0]{latex};},
 %%mark=at position 0.88 with {\arrow[blue,rotate=-180]{latex};}
%        mark=between positions 0.13 and 0.37 step 0.2 with {\arrow{<};},        mark=between positions 0.43 and 0.77 step 0.16 with {\arrow{>};},
%        mark=at position 0.9 with {\arrow{<};}
      }}
        ]{-sin(deg(x))}node[right,pos=0.9]{$f(y)$};
\node[below,text=black,font=\Large] at (15,3) {$f(y)$};
%\draw[-latex](0,0)--(5,0)node[right]{\emph{Old} latex arrow};
\node[text=red,font=\Large,anchor=north east] at (0,0) {$0$};
\node[text=red,font=\Large,anchor=south east] at (pi,0) {$\theta
$};
\node[text=red,font=\Large,anchor=south west] at (2*pi,0) {$\kappa$};
\draw[black,dotted] (pi,0) -- (pi,-2) node [above left,xshift=0.3em] {\small{extinction}};
\end{axis}
\end{tikzpicture}
\end{document}

Answer