我想要绘制下图：
我尝试了以下代码：
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{tikzpicture}[decoration={markings,
mark=at position 1cm with {\arrow[line width=1pt]{stealth}},
mark=at position 4.5cm with {\arrow[line width=1pt]{stealth}},
mark=at position 7cm with {\arrow[line width=1pt]{stealth}},
mark=at position 9.5cm with {\arrow[line width=1pt]{stealth}}
}]
\draw[thick, ->] (-6,0) -- (6,0) coordinate (xaxis);
\draw[thick, ->] (0,0) -- (0,6) coordinate (yaxis);
\node[above] at (xaxis) {$\mathrm{Re}(s)$};
\node[right] at (yaxis) {$\mathrm{Im}(s)$};
\path[draw,blue, line width=0.8pt, postaction=decorate] (-4,4)
-- node[midway, above, black] {$C_1$} (4,4)
-- node[midway, right, black] {$C_N$}(4,0)
-- node[midway, left, black] {$C_2$} (-4,0)
-- node[midway, above, black] {$C_N$}(-4,4);
\end{tikzpicture}
\end{document}
我得到：
我如何才能正确获得箭头的方向和 $x$ 轴上的标记？
谢谢您的帮助！！
答案1
作为一种“破解”方法来修复它......你可以使用\arrowreversed而不是\arrow。
我还移动了声明节点的位置，以便更清楚地表明您可以在路径的同一位置添加多个节点。使用位置选项，您可以精确控制放置节点的位置。
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{tikzpicture}[decoration={markings,
mark=at position 1cm with {\arrowreversed[line width=1pt]{stealth}},
mark=at position 4.5cm with {\arrowreversed[line width=1pt]{stealth}},
mark=at position 7cm with {\arrowreversed[line width=1pt]{stealth}},
mark=at position 9.5cm with {\arrowreversed[line width=1pt]{stealth}}
}]
\draw[thick, ->] (-6,0) -- (6,0) coordinate (xaxis);
\draw[thick, ->] (0,0) -- (0,6) coordinate (yaxis);
\node[above] at (xaxis) {$\mathrm{Re}(s)$};
\node[right] at (yaxis) {$\mathrm{Im}(s)$};
\path[draw,blue, line width=0.8pt, postaction=decorate]
(-4,4)
-- (4, 4) node[midway, above right, black] {$C_1$}
-- (4, 0) node[midway, right, black] {$C_N$} node[below, black] {$R$}
-- (-4,0) node[midway, below, black] {$C_2$} node[below, black] {$-R$}
-- (-4,4) node[midway, left, black] {$C_N$};
\end{tikzpicture}
\end{document}
