[Tex/LaTex] Tikz-Tree: Arrow-style depending on parent node

tikz-pgftikz-trees

I have drawn a tree in tikz with different styles for nodes (this simplified example has nodes with style a or b). The arrows from nodes to childs are always the same and I would like to apply different styles to the edge/arrow depending on the style of the parent node.

\begin{tikzpicture}[
    a/.style={circle, draw=black, edge from parent/.style=myEdge1},
    b/.style={rectangle, draw=red, edge from parent/.style=myEdge2},
    myEdge1/.code={
        \draw[-] \tikzparentnode -- \tikzchildnode;
    }
    myEdge2/.code={
        % No edge or applying a different style
    }
]
\node[a]{}
    child {node[a] {}}
    child {
        node[b] {no arrows from this node}
        child {node[a] {no arrow to this node}}
        child {node[b] {no arrow to this node}}
    }
    child {node[a] {}}
;
\end{tikzpicture}

This is how it is supposed to look:

example

First of all, the code above does not work when edge from parent/.style=myEdge1 is defined within a style (a or b). It only works when I put it right behind the child, i.e. child[edge from parent/.style=myEdge1]. Second (and this would probably solve the first issue), I would rather need edge to child than edge from parent since the style of the parent shall decide whether an arrow has to be drawn or not. But there is no such thing as edge to child in the tikz documentation. Is there an easier solution than telling each child whether it should have an arrow from its parent or not such that tikz automatically adopts the edge style from the style of the parent node?

Best Answer

You can set an option that only applies to the children, if you use the every child style.

The no edge from this parent style is setup in a way that the children of the child it is used on doesn’t draw the edge.

Instead of draw one you can set any other option an edge can have. This does not include a \draw command!

For edges in a tree there is a special key that sets the path: edge from parent path.

The default path is

(\tikzparentnode\tikzparentanchor) -- (\tikzchildnode\tikzchildanchor)

Code

\documentclass[tikz,convert=false]{standalone}
\begin{document}
\begin{tikzpicture}[
  no edge from this parent/.style={
    every child/.append style={
      edge from parent/.style={draw=none}}},
  a/.style={circle, draw=black},
  b/.style={rectangle, draw=red},
]
\node[a] {}
  child {node[a] {}}
  child[no edge from this parent] {node[b] {no}
    child {node[a] {no}}
    child {node[b] {no}}
  }
  child {node[a] {}}
;
\end{tikzpicture}
\end{document}

Output

enter image description here

Related Solutions

[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).

[Tex/LaTex] Child node from edge from parent node

You can for example start a new tree. Note below I added the x_1^L node by using

\path (11) -- node (H) {$\bm{x}^{L}_{1}$} (12);

instead of the edge from parent node with some x- and y-shift I guess you found by trial and error. The next tree can then be initiated with

\node [below=3mm] at (H)

You also seem to be consistently use solid node,fill=white, instead of using hollow node directly, so I modified all of those as well.

\documentclass[border=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{arrows,positioning,decorations.pathreplacing, trees}
\usepackage{bm}

\begin{document}
% Node styles
\tikzset{
% Two node styles for game trees: solid and hollow
solid node/.style={circle,draw,inner sep=1.5,fill=black},
hollow node/.style={circle,draw,inner sep=1.5,fill=white}
}
\begin{tikzpicture}[
 scale=1.5,font=\footnotesize,
 level 1/.style={level distance=10mm,sibling distance=30mm},
 level 2/.style={level distance=15mm,sibling distance=10mm},
 level 3/.style={level distance=15mm,sibling distance=10mm}
]
% The Tree
\node(0)[solid node,label=above:{Nature}]{} 
child{node(1)[hollow node]{$L$}
child{[black] node(11)[hollow node]{}}
child{[black] node(12)[hollow node]{}}
edge from parent node[left]{$p$}
}
child{node(2)[hollow node]{$H$}
child{[black] node(41)[hollow node, ]{}}
child{[black] node(42)[hollow node,]{}}
edge from parent node[right]{$1-p$}
};
% information set
  \draw[dashed,bend right](11)to(12);
  \draw[dashed,bend right](41)to(42);

\path (11) -- node (H) {$\bm{x}^{L}_{1}$} (12);
\path (41) -- node {$\bm{x}^{H}_{1}$} (42);

% scope env to locally redefine level 1 style
\begin{scope}[
  level 1/.style={sibling distance=10mm}
]
\node [below=4mm,hollow node] at (H) {$H$}
   child{ node[hollow node] {}
          edge from parent node[left] {$A$}
        }
   child{ node[hollow node] {} 
          edge from parent node[right] {$R$}
         }
;
\end{scope}
\end{tikzpicture}
\end{document}

Best Answer

Code

Output

Related Solutions

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

[Tex/LaTex] Child node from edge from parent node

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