[Tex/LaTex] avoid overlapping of labels and arcs in Tikz

tikz-pgf

I'm using chains to draw a simple Markov chain. I used \draw and \path to manually add arcs between nodes. But the labels and arcs overlap badly although I used auto location for labels. Is there a way to let Tikz do this automatically? Manually adjusting distances is possible but I believe Tikz is more powerful than I know.

enter image description here

\documentclass{standalone}

\usepackage{tikz}
\begin{document}
\usetikzlibrary{automata,chains}
\begin{tikzpicture}[start chain=going right]
\node[state,on chain] (-2) {-2};
\node[state,on chain] (-1) {-1};
\node[state,on chain] (0) {0};
\node[draw=red,fill=red,state,on chain] (+1) {+1};
\node[draw=red,fill=red,state,on chain] (+2) {+2};

\draw[->] (-1) to node[auto] {$P(0)$}(-2);
\path[->] (-1) edge  [loop above] node[auto] {$P(1)$} ();
\draw[->] (-1) to node[auto] {$P(2)$}(0);
\draw[->] (-1) to[bend right] node[auto] {$P(3)$}(+1);
\draw[->] (-1) to[bend right] node[auto] {$P(4)$}(+2);

\draw[->] (+1) to node[above]{$1$} (0);
\draw[->] (+2) to[bend right] node[above]{$1$} (0);
\end{tikzpicture}
\end{document}

Best Answer

Here is another approach.

In some cases when you have lots of nearby arcs, it is not a bad idea to put the labels on the arcs themselves. Here is an example from some previous work of mine:

My example figure.

With this in mind, here is how I would typeset your figure:

\documentclass[margin=2mm]{standalone}

\usepackage{tikz}
\usetikzlibrary{automata,chains}

\begin{document}

\begin{tikzpicture}[start chain=going right]
  \tikzset{%
    in place/.style={
      auto=false,
      fill=white,
      inner sep=2pt,
    },
  }
  %
  \node[state,on chain]                   (-2) {$-2$};
  \node[state,on chain]                   (-1) {$-1$};
  \node[state,on chain]                   (0)  {$0$};
  \node[draw=red,fill=red,state,on chain] (+1) {$+1$};
  \node[draw=red,fill=red,state,on chain] (+2) {$+2$};
  \draw[->, auto]
    (-1) edge node[swap] {$P(0)$} (-2)
    (-1) edge[loop above] node {$P(1)$} ()
    (-1) edge node {$P(2)$} (0)
    (-1) edge[bend right=35] node[pos=0.7, in place] {$P(3)$} (+1)
    (-1) edge[bend right=35] node[pos=0.7, in place] {$P(4)$} (+2)
    (+1) edge node[swap] {$1$} (0)
    (+2) edge[bend right] node[swap] {$1$} (0)
    ;
\end{tikzpicture}

\end{document}

Please note that

  • I have grouped all your edges into one \draw operation;
  • because of this, I can specify the auto option just once, and
  • swap edges that appear on the "wrong" side, while
  • the in place style (defined at the top of the figure) disables auto for a single node.

I also increased the bend angle a bit (from the default of 30 degrees) to give your arcs a bit more breathing room.

Finally, note that your numbers should be typeset in math mode. Compare the $-1$ in my figure to the -1 in your original.

My rendering of your example.

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