Figure in Tikz (2 state Markov)

Question

I would like to make the following figure in Tikz:

I have tried using the code here, but I did not succeed unfortunately.

Can anyone provide me some code to make such a picture?

Thanks in advance.

Which code there did you try? The answer there provides more than one method of drawing the image. And in what sense did you not succeed? Can we please see what you've got? It is a lot easier to help if we know what problem you've run into and can work from your specific starting point ;). — cfr, Sep 13 '15 at 20:36

score 6 · Accepted Answer · answered Sep 13 '15 at 21:39

One fairly simple-minded option:

\documentclass[tikz,border=10pt,multi]{standalone}
\usetikzlibrary{positioning,arrows.meta,,bending}
\begin{document}
  \begin{tikzpicture}
    [
      >/.tip={Triangle[length=7.5pt,width=5pt,bend]},
      line width=1pt,
      my circle/.style={minimum width=10mm, circle, draw},
      my label/.style={above=10pt, anchor=mid}
    ]
    \node (1) [my circle] {$1$};
    \node (2) [my circle, right=75pt of 1] {$2$};
    \path [postaction={draw, {>[sep=5pt,reversed]}-{<[sep=5pt]}}, draw] (1) -- (2) node [very near start, my label] {$\alpha$}  node [very near end, my label] {$\beta$} ;
    \path [->, draw] (2.south east) arc (-135:135:5mm) node [near end, my label] {$1-\beta$};
    \path [->, draw] (1.south west) arc (-45:-315:5mm) node [near end, my label] {$1-\alpha$};
  \end{tikzpicture}
\end{document}

@MyUserIsThis Just because I didn't use automata or loops or anything fancy like that ;). — cfr, Sep 14 '15 at 10:08

sergej · Answer 2 · 2015-09-14T13:07:37.917

Maybe something like this?

\documentclass[tikz,border=10pt]{standalone}
\usetikzlibrary{positioning}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{decorations.text}

\begin{document}
\begin{tikzpicture}[
  node distance = 1cm and 2cm, >=latex,
  state/.style={draw, thick, circle, minimum size=8mm, inner sep=0pt},
  transitionA/.style args={#1}{very thick, ->, postaction={decorate},
    decoration={markings,
      mark=at position .8 with {\node[anchor=south,yshift=1pt] {#1};}}},
  transitionB/.style args={#1}{very thick, postaction={decorate},
    decoration={markings,
      mark=at position .26 with {\arrow{>}},
      mark=at position .2 with {\node[anchor=south,yshift=1pt] {#1};}}}
  ]

  \node[state] (1) {$1$};
  \node[state,right=of 1] (2) {$2$};

  \draw [transitionA={$1-\alpha$}] (1.south west) arc (-45:-315:4mm);
  \draw [transitionA={$1-\beta$}]  (2.south east) arc (-135:135:4mm);
  \draw [transitionB={$\alpha$}]   (1.east) -- (2.west);
  \draw [transitionB={$\beta$}]    (2.west) -- (1.east);
\end{tikzpicture}
\end{document}

Version 2 (Edit: using automata library)

\documentclass[tikz,border=10pt]{standalone}
\usetikzlibrary{arrows,automata}

\begin{document}
\begin{tikzpicture}[node distance=2cm,->,>=latex,auto,
  every edge/.append style={thick}]
  \node[state] (1) {$1$};
  \node[state] (2) [right of=1] {$2$};  
  \path (1) edge[loop left]  node{$1-\alpha$} (1)
            edge[bend left]  node{$\alpha$}   (2)
        (2) edge[loop right] node{$1-\beta$}  (2)
            edge[bend left] node{$\beta$}     (1);
\end{tikzpicture}
\end{document}

Zarko · Answer 3 · 2015-09-14T06:35:23.983

Try the following:

    \documentclass[tikz]{standalone}
    \usetikzlibrary{automata,decorations.markings,positioning}

    \begin{document}
        \begin{tikzpicture}[
                >=latex,
      decoration = {markings,
                    mark=at position .3 with {\arrow {>}},
                    mark=at position .7 with {\arrowreversed {>} }
                  },
                node distance=33mm]
    \node[state]    (n1) {1};
    \node[state]    (n2) [right=of n1] {2};
    \path[->,every loop/.style={looseness=8}]
   (n1) edge [postaction={decorate}] node [pos=0.3,above] {$\alpha$}
                                     node [pos=0.7,above] {$\beta$}  (n2)
   (n1) edge [in=210,out=150,loop] node[above=11pt] {$1-\alpha$} ()
   (n2) edge [in=-30,out=30, loop] node[above=11pt] {$1-\beta$}  ();
        \end{tikzpicture}
    \end{document}

Edit: I change the loop appearance with defined in and out angle for loops, and simplify ling between state.

Figure in Tikz (2 state Markov)

3 Answers3

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