[Tex/LaTex] TikZ: Drawing directed trees using tree layout, child{…}-syntax and lualatex

luatextikz-trees

There seems to be no way to draw directed edges using the new (?) tree graph layout and the child-syntax.

\documentclass{standalone}

\usepackage{tikz}
\usepackage{lmodern}
\usetikzlibrary{arrows.meta}
\usetikzlibrary{graphs}
\usetikzlibrary{graphdrawing}
\usegdlibrary{trees}

\tikzset{
  ->, % doesn't work
  nodes={draw, circle, minimum size = .5cm},
  >=Stealth[], % doesn't work
}

\begin{document}

\tikz[tree layout,
edge from parent/.style={draw,-latex}, % doesn't work
-> % doesn't work
] {
  \node {$\land$}
  child {
    node {$\lnot$}
    child {
      node {$a$}
    }
  }
  child {
    node {$\rightarrow$}
    child {
      node {$b$}
    }
    child {
      node {$c$}
    }
  };
}

\end{document}

Prove me wrong!

EDIT: I think I do use the new graph layout engine because using the conventional tikzpicture environment, the tree looks like this:

Best Answer

If you are using graph syntax, directed edges are specified within the tree specification itself. For example,

{ r -> a }

indicates a directed edge from r to a.

The whole point of the graph drawing libraries is that you specify the relationships and let Lua figure out the detailed structure.

Using this syntax, the directed edges are no problem. And, thanks to Gonzalo Medina's comment, I'm now able to get mathematical content into the nodes as well.

So, for example, using the graph syntax, I can produce

using this specification:

% modified from Gonzalo Medina's comment (below)
\tikz [tree layout] \graph [math nodes, nodes={draw, circle, minimum size = .5cm}, sibling sep=0pt]
{aaaa [as=$\land$] -> {aa [as=$\lnot$] -> a , aaa [as=$\rightarrow$] -> {b , c}} };

If your graphs are all trees i.e. have a single root, you might like to use a specialised tree-drawing package such as forest, qtree or tikz-qtree instead. If they are not all trees, you can still do this but only by tricking the package into thinking you are really drawing a tree, so it gets more complicated.

For your tree, for example, the forest specification looks like this:

\begin{forest}
  for tree={
    edge = {->},
    circle,
    minimum size=5mm,
    inner sep=0pt,
    draw,
    math content,
    tier/.wrap pgfmath arg={tier #1}{level()},
    anchor=center
  },
  [\land
    [\lnot
      [a]
    ]
    [\rightarrow
      [b]
      [c]
    ]
  ]
\end{forest}

Here including maths in the nodes is a bit more straightforward, but obviously you have to specify the precise structure of the tree you want - you can't just specify the relationships as you can with the graph drawing libraries.

Complete Code

\documentclass[tikz,multi,border=10pt]{standalone}
\usetikzlibrary{arrows.meta,graphs,graphdrawing}
\usegdlibrary{trees}
\usepackage{forest}
\tikzset{
  >=Stealth[], % does work
}

\begin{document}

% modified from 406 of manual, and using Gonzalo Medina's comment (below)
\tikz [tree layout] \graph [math nodes, nodes={draw, circle, minimum size = .5cm}, sibling sep=0pt]
{aaaa [as=$\land$] -> {aa [as=$\lnot$] -> a , aaa [as=$\rightarrow$] -> {b , c}} };

\begin{forest}
  for tree={
    edge = {->},
    circle,
    minimum size=5mm,
    inner sep=0pt,
    draw,
    math content,
    tier/.wrap pgfmath arg={tier #1}{level()},
    anchor=center
  },
  [\land
    [\lnot
      [a]
    ]
    [\rightarrow
      [b]
      [c]
    ]
  ]
\end{forest}

\end{document}

EDIT

If you prefer to stick to the old syntax for trees, you can do that so long as you don't mix it in problematic ways with the graph drawing environment.

\documentclass[tikz,border=10pt]{standalone}
\usetikzlibrary{arrows.meta}
\tikzset{
  my tree/.style={
    ->,
    nodes={draw, circle, minimum size = .5cm},
    >=Stealth[],
  },
}
\begin{document}
\tikz [ my tree ]
  \node {$\land$}
  child {
    node {$\lnot$}
    child {
      node {$a$}
    }
  }
  child {
    node {$\rightarrow$}
    child {
      node {$b$}
    }
    child {
      node {$c$}
    }
  };
\end{document}

I don't get the problems with overlapping nodes shown in your screenshot provided I do not load the graphdrawing TikZ library:

Related Solutions

[Tex/LaTex] drawing tree using tikz, child overlap

Maybe not as nice looking a tree, but a lot faster to input. The tikz-qtree package is designed to optimize the spacing between nodes.

\documentclass{article}
\usepackage{tikz-qtree,tikz-qtree-compat}
\begin{document}
\begin{tikzpicture}[level 1/.style={level distance=1.5cm}]
\Tree
[.country 
  [.name France ] [.city Paris ] [.region 
                      [.name {Nord-Pas de Calais} ] 
                      [.population 3996 ] 
                      [.city Lille  ]
                   ] 
                   [.region 
                       [.name {Valle du Rhone } ] 
                      [.city Lyon ] 
                      [.city Valence ]
                  ]
]
\end{tikzpicture}
\end{document}

output of code

[Tex/LaTex] Styles in TikZ trees not working as expected

Just a quick demonstration with Forest. The major advantages of Forest lie in its power, flexibility and concise syntax. Regularities in content and styling can be turned into automated configuration rules and trees themselves can be specified very concisely. Since Forest is based on TikZ, the power of the host package is also available.

For example,

\begin{forest}
  bordered tree,
  [
    [x, border
      [x1, acc, for descendants=border
        [][][]
      ]
      [x2, rej]
      [x3, for children=border
        [][][]
      ]
    ]
  ]
\end{forest}

specifies the target tree:

while the following partly explains the first and partly shows one or two additional tricks,

\begin{forest}
  bordered tree,
  [
    [x, border, normal
    [x1, acc, for descendants=border, label=left:\texttt{for descendants}
        [][.,label=left:bordered children [][]][]
      ]
      [x2, rej]
      [x3, normal, for children=border, label=right:\texttt{for children}
        [][.,label=right:unbordered children [][]][, for current and ancestors={edge+=blue}]
      ]
    ]
  ]
\end{forest}

which produces:

Complete code:

\documentclass[border=10pt]{standalone}
\usepackage{forest}
\forestset{
  declare boolean={border}{0},
  bordered tree/.style={
    for tree={
      minimum size=4mm, 
      inner sep=0.5mm,
      edge+={semithick},
      semithick,
    },
    before typesetting nodes={
      where border={
        edge+={dashed, draw},
      }{},
      where={isodd(n_children)}{
        tempcounta/.process={
          Ow+n {n children}{(##1+1)/2}
        },
        for n={
          >  R {tempcounta} % doesn't work to plug the above in directly ??'
        }{calign with current edge},
      }{},
      where content={}{}{normal},
    },
  },
  /tikz/.cd,
  normal/.style={circle,draw},
  invis/.style={draw=none},
  acc/.style={circle,thick,draw=green!50,fill=green!2},
  rej/.style={circle,thick,draw=red!50,fill=red!20},
}
\begin{document}
\begin{forest}
  bordered tree,
  [
    [x, border
      [x1, acc, for descendants=border
        [][][]
      ]
      [x2, rej]
      [x3, for children=border
        [][][]
      ]
    ]
  ]
\end{forest}
\begin{forest}
  bordered tree,
  [
    [x, border, normal
    [x1, acc, for descendants=border, label=left:\texttt{for descendants}
        [][.,label=left:bordered children [][]][]
      ]
      [x2, rej]
      [x3, normal, for children=border, label=right:\texttt{for children}
        [][.,label=right:unbordered children [][]][, for current and ancestors={edge+=blue}]
      ]
    ]
  ]
\end{forest}
\end{document}