[Tex/LaTex] How to change the position of the initial text in TikZ automata

automatapositioningtikz-pgf

It seems PGF manual for v1.18 doesn't cover the case on how to change the position of the initial text relative to the initial transition. Accoring to the PGF manual section 19.3 the parameters of initial state allow me to change the position of the text:

– initial where=⟨direction⟩ set the place where the text should be shown. Allowed values are above, below, left, and right.

This, however, changes the position of both arrow and the text, for instance

\begin{tikzpicture}[>=latex, initial text={start}, initial where=left]
\node[state,initial] (q_0);
\end{tikzpicture}

results in this:

current

What I'd like to have is the text positioned relative to the arrow, e.g. above:

goal

Is there a standard way to achieve this?

Best Answer

I have not seen that this feature is supported by the library automata. But the arrow with text can be disabled and the drawing can be done with usual TikZ means:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{automata}

\begin{document}

\begin{tikzpicture}[>=latex]
  \node[state] (q_0) {$q_0$};
  \draw[<-] (q_0) -- node[above] {start} ++(-2cm,0);
\end{tikzpicture}

\end{document}

Related Solutions

[Tex/LaTex] Position text next to rectangle in TikZ

The manual is indeed long but it's very well structured so you can skip many irrelevant parts. For this specific example, you can use a node and put labels around it.

\documentclass{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\node[fill=black!40!white,
      thick,
      draw,
      minimum height=0.5cm,
      minimum width=3.2cm,
      label=0:end,%< -- This uses angle zero degree on the border for the location
      label=west:start %< -- This uses an anchor of the node for the location
] at (0,1.5) {cp};
\end{tikzpicture}
\end{document}

enter image description here

[Tex/LaTex] How to avoid superfluous space in the initial state of a tikz automaton

It's because when you clear the text of the initial node you don't actually decrease the node size. I've added a draw to the node options to make it obvious that your guess is correct:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{automata}
\tikzset{initial text={}}
\makeatletter
\tikzstyle{initial by arrow}=   [after node path=
{
  {
    [to path=
    {
      [->,double=none,every initial by arrow]
      ([shift=(\tikz@initial@angle:\tikz@initial@distance)]\tikztostart.\tikz@initial@angle)
          node [shape=rectangle,anchor=\tikz@initial@anchor,draw] {\tikz@initial@text}
        -- (\tikztostart)}]
    edge ()
  }
}]
\makeatother

\begin{document}

\begin{tikzpicture}
    \node[state, initial] {};
    \draw[red, dashed] (current bounding box.south west) rectangle (current bounding box.north east);
\end{tikzpicture}

\end{document}

enter image description here

Instead of draw you can put an inner sep=0 which is a good approximation, or delete the node or add overlay to keep the node but not include it in the bounding box.

Best Answer

Related Solutions

[Tex/LaTex] Position text next to rectangle in TikZ

[Tex/LaTex] How to avoid superfluous space in the initial state of a tikz automaton

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