树节点对齐错误

Question

我有点思维混乱，希望有人能帮我。我正在尝试绘制以下树，但遇到了两个问题：

1. 以最左侧“doc”为根的子树应以节点 &o2 为根。不知道为什么会这样。
2. 边缘应有方向。

这是我的 MWE：

\documentclass[margin=1mm,xcolor=pdftex,dvipsnames]{standalone}

\usepackage{tikz}

\tikzset{every picture/.style={/utils/exec={\sffamily}},>=latex,align=center,font={\fontsize{10pt}{12}\selectfont}}

\begin{document}

\begin{tikzpicture}[level distance=1.5cm,
level 1/.style={sibling distance=3.5cm},
level 2/.style={sibling distance=2cm},
tree node/.style={circle,draw,inner sep=1pt,minimum width=0.5cm},
every child node/.style={tree node}]

\node[circle,draw] {\&o1}
child {node {\&o2} edge from parent node[midway] {doc}
    child {node {\&o3} edge from parent node[midway] {authors}}
    child {node {\&o6} edge from parent node[midway] {title}}
}
child {node {\&o22} edge from parent node[midway] {doc}}
child {node {\&o34} edge from parent node[midway] {doc}}
;
\end{tikzpicture}

\end{document}

非常感谢您的帮助。

Answer 1

你把节点设为文档节点的子节点，这就是你得到的。如果你将边移到两个子节点之后，你会得到

\documentclass[margin=1mm,xcolor=pdftex,dvipsnames]{standalone}

\usepackage{tikz}

\tikzset{every picture/.style={/utils/exec={\sffamily}},>=latex,align=center,font={\fontsize{10pt}{12}\selectfont}}

\begin{document}

\begin{tikzpicture}[level distance=1.5cm,
level 1/.style={sibling distance=3.5cm},
level 2/.style={sibling distance=2cm},
tree node/.style={circle,draw,inner sep=1pt,minimum width=0.5cm},
every child node/.style={tree node},
every path/.append style={-latex}]

\node[circle,draw] {\&o1}
child {node {\&o2} 
    child {node {\&o3} edge from parent node[midway,above,sloped] {authors}} 
    child {node {\&o6} edge from parent node[midway,above,sloped] {title}} 
    edge from parent node[midway,above,sloped] {doc} }
child {node {\&o22} edge from parent node[midway,above,sloped] {doc}}
child {node {\&o34} edge from parent node[midway,above,sloped] {doc}}
;
\end{tikzpicture}

\end{document}

不过，我建议使用forest，这可能更直观。

\documentclass[tikz,border=3.14mm]{standalone}
\usepackage{forest}
\begin{document}
\forestset{el/.style={edge label={node[above,pos=0.5,sloped,font=\sffamily]{#1}}}}
\begin{forest}
    for tree={circle,draw,l+=2em,s sep=5em,font=\sffamily,edge=-latex}
    [\&o1 
     [\&o2,el=doc
      [\&o3,el=authors]
      [\&o6,el=title]
     ]
     [\&o22,el=doc]
     [\&o34,el=doc]
    ]
\end{forest}
\end{document}