我正在尝试绘制一个状态图，尽管许多类似的状态图都可以正常工作，但这个特定的状态图似乎无缘无故地出现了这个错误。
我编译时得到的错误pdflatex是
! Package tikz Error: (, +, coordinate, pic, or node expected.
See the tikz package documentation for explanation.
Type H <return> for immediate help.
...
l.21 \draw[input] (start) to \node
[above,sloped] {a} (a);
这是我的代码
\documentclass[fleqn]{article}
\usepackage{tikz} % for diagrams
\usetikzlibrary{positioning}
\usetikzlibrary{arrows}
\begin{document}
\begin{tikzpicture}[
state/.style={circle, draw=blue!60, fill=blue!5, very thick, node distance=1.5cm},
start/.style={name=start},
input/.style={->, thick, shorten >= 1mm, shorten <= 1mm},
]
\node[state, start] {\(q_0\)};
\node[state, above right=of start] (a) {\(q_1\)};
\node[state, below right=of start] (b) {\(q_2\)};
\draw[input] (start) to \node[above,sloped] {a} (a);
\draw[input] (start) to \node[below,sloped] {b} (b);
\draw[input, loop above] (start) to \node[above] {c} (start);
\draw[input] (start.west)+(-1cm,0) to (start.west);
\end{tikzpicture}
\end{document}
一个类似的、可以工作的图表的例子是
\documentclass[fleqn]{article}
\usepackage{tikz} % for diagrams
\usetikzlibrary{positioning}
\usetikzlibrary{arrows}
\begin{document}
\begin{tikzpicture}[
state/.style={circle, draw=blue!60, fill=blue!5, very thick, node distance=1.5cm},
start/.style={name=start},
input/.style={->, thick, shorten >= 1mm, shorten <= 1mm},
]
\node[state, start] {\(q_0\)};
\node[state, right=of start] (odd) {\(q_1\)};
\draw[input, bend left=40] (start) to node[below] {a,b,c} (odd);
\draw[input, bend left=40] (odd) to node[above] {a,b,c} (start);
\end{tikzpicture}
\end{document}
答案1
你不应该在路径内使用\nodebut (另请参阅nodeZarko 的评论，我刚才看到了。）
\documentclass[fleqn]{article}
\usepackage{tikz} % for diagrams
\usetikzlibrary{positioning}
\usetikzlibrary{arrows}
\begin{document}
\begin{tikzpicture}[
state/.style={circle, draw=blue!60, fill=blue!5, very thick, node distance=1.5cm},
start/.style={name=start},
input/.style={->, thick, shorten >= 1mm, shorten <= 1mm},
]
\node[state, start] {\(q_0\)};
\node[state, above right=of start] (a) {\(q_1\)};
\node[state, below right=of start] (b) {\(q_2\)};
\draw[input] (start) to node[above,sloped] {a} (a);
\draw[input] (start) to node[below,sloped] {b} (b);
\draw[input, loop above] (start) to node[above,midway] {c} (start);
\draw[input] (start.west)+(-1cm,0) to (start.west);
\end{tikzpicture}
\end{document}
quotes如果你不喜欢这个语法，你可以在这里使用node。（但是如果你添加了 babel 包，请记得也添加\usetikzlibrary{babel}。）
\documentclass[fleqn]{article}
\usepackage{tikz} % for diagrams
\usetikzlibrary{positioning}
\usetikzlibrary{quotes}
\begin{document}
\begin{tikzpicture}[
state/.style={circle, draw=blue!60, fill=blue!5, very thick, node distance=1.5cm},
start/.style={name=start},
input/.style={->, thick, shorten >= 1mm, shorten <= 1mm},
]
\node[state, start] {\(q_0\)};
\node[state, above right=of start] (a) {\(q_1\)};
\node[state, below right=of start] (b) {\(q_2\)};
\draw[input] (start) to["a" sloped] (a);
\draw[input] (start) to["b" sloped] (b);
\draw[input, loop above] (start) to["c"] (start);
\draw[input] (start.west)+(-1cm,0) to (start.west);
\end{tikzpicture}
\end{document}
答案2
扩展我的评论，作为对@Schrödinger 的猫答案的补充，基于tikz库automata：
\documentclass[fleqn]{article}
\usepackage{tikz} % for diagrams
\usetikzlibrary{automata,
positioning,
quotes}
\begin{document}
\begin{tikzpicture}[auto,
node distance = 11mm and 11mm,
state/.style = {circle, draw=blue!60, very thick, fill=blue!5,
minimum size=2em, inner sep=0pt},
shorten > = 1mm, shorten < = 1mm,
thick,
initial text = , initial distance = 9mm,
every edge quotes/.style = {sloped}
]
\node (start) [state, initial] {\(q_0\)};
\node (a) [state, above right=of start] {\(q_1\)};
\node (b) [state, below right=of start] {\(q_2\)};
%
\path[->] (start) edge["$a$"] (a)
(start) edge["$b$"] (b)
(start) edge[loop above,looseness=10,"$c$"] (start);% default looseness=8
\end{tikzpicture}
\end{document}
