[Tex/LaTex] Tikz: Simple decision tree (node connections)

node-connectionsnodestikz-pgf

I am trying to reproduce the following

So far I got this:

\begin{tikzpicture}[]
\small
\node[] (AB) {$A \succeq B$};
\node[]{}
    child{node[chance]{C}
      edge from parent
        node[above]{1-p}    
                }
    child{node[chance]{A} 
      edge from parent
          node[below]{p}
        };
\end{tikzpicture}

My basic problem is to label and connect simples nodes. So what is the command for "place this node A \succeq B left to the decision tree with decent distance"? Thank you very much.

Best Answer

Here are two options showing how to produce the trees using two of the most popular packages for tree generation; the first one using the forest package and the second one using tikz-qtree:

\documentclass{article}   
\usepackage{forest}
\usepackage{tikz-qtree}

\begin{document}

\[
A \succeq B
\Rightarrow
\begin{forest}
baseline,
for tree={grow=0,parent anchor=east,l sep=35pt} 
[
  [C,edge label={node[sloped,pos=0.5,below,font=\scriptsize]{$1-p$}}]
  [A,edge label={node[sloped,pos=0.5,above,font=\scriptsize]{$p$}}]
] 
\end{forest}
\succeq
\begin{forest}
baseline,
for tree={grow=0,parent anchor=east,l sep=35pt} 
[
  [C,edge label={node[sloped,pos=0.5,below,font=\scriptsize]{$1-p$}}]
  [B,edge label={node[sloped,pos=0.5,above,font=\scriptsize]{$p$}}]
] 
\end{forest}
\]

\[
A \succeq B
\Rightarrow
\begin{tikzpicture}[baseline,grow=right,level distance=35pt]
\Tree[
  \edge node[sloped,pos=0.5,below,font=\scriptsize]{$1-p$}; C
  \edge node[sloped,pos=0.5,above,font=\scriptsize]{$p$}; A
] 
\end{tikzpicture}
\succeq
\begin{tikzpicture}[baseline,grow=right,level distance=35pt]
\Tree[
  \edge node[sloped,pos=0.5,below,font=\scriptsize]{$1-p$}; C
  \edge node[sloped,pos=0.5,above,font=\scriptsize]{$p$}; B
] 
\end{tikzpicture}
\]

\end{document}

The result:

Related Solutions

[Tex/LaTex] How to modify the distance between branches when drawing trees using TiKZ

You can change the sibling distance for each level of the tree individually, using level <number>/.style={sibling distance=<value>}:

\documentclass[a4paper,landscape]{scrartcl}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}[
    auto,
    level 1/.style={sibling distance=40mm},
    level 2/.style={sibling distance=10mm}]
    \node [circle,draw] (z){0}
        child {
            node[circle,draw] (a) {1}
            child { 
                node[circle,draw] (c) {5} 
            }
            child { 
                node[circle,draw] (d) {5} 
            }   
            child { 
                node[circle,draw] (e) {5} 
            }   
            child { 
                node[circle,draw] (f) {5} 
            }   
        }
        child {
            node[circle,draw] (b) {2}
        }
        ;
    \end{tikzpicture}
\end{document}

[Tex/LaTex] Changing the indentation of a Tikz tree

Let's provide a different example which shows better your problem:

% Assumming preamble as provided in the question
    \tikzset{
    dirtree/.style={
      growth function=\dirtree@growth,
      every node/.style={anchor=north},
      every child node/.style={anchor=west},
      edge from parent path={(\tikzparentnode\tikzparentanchor) |- (\tikzchildnode\tikzchildanchor)}
  }
}
\makeatother
\begin{document}
\begin{tikzpicture}[dirtree]
\node {toplevel} 
    child { node {Foobarish}
            child { node  {foobar} 
                    child { node {foo}} 
                  }
            child { node  {foo} 
                    child {node {foo} } 
                  }
            child { node  {bar} }
    }
    child { node {Bar}
        child { node {foo} }
        child { node {foo} }
    };
\end{tikzpicture}

The output is:

Output

This shows not only the issue you mention, but also that the vertical stems in each branch are not aligned (the branch from Foobarish is not aligned with the branch from Bar). This problem will be also solved with a proper parent anchor (and growth parent anchor) which does not depend on the size of the parent. In this case south west is the best choice.

The following style solves all these issues, and provides a very compact version of the tree.

\tikzset{
  dirtree/.style={
    growth function=\dirtree@growth,
    growth parent anchor=south west,
    parent anchor=south west,
    every child node/.style={anchor=west},
    edge from parent path={([xshift=2ex] \tikzparentnode\tikzparentanchor) 
                           |- (\tikzchildnode\tikzchildanchor)}
  }
}

Final result

Thanks to Andrew Stacey and Jake for their useful comments about the need to set also growth parent anchor (their comments below refer to an early version of this answer).

Best Answer

Related Solutions

[Tex/LaTex] How to modify the distance between branches when drawing trees using TiKZ

[Tex/LaTex] Changing the indentation of a Tikz tree

Related Question