决策树格式化（边合并）

Question

我正在尝试绘制一个结构如下的决策树：

这是我目前所拥有的：

\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
 [
    grow                    = right,
    sibling distance        = 6em,
    level distance          = 10em,
    edge from parent/.style = {draw, -latex},
    every node/.style       = {font=\footnotesize},
    %sloped
  ]
\node{root}
child {node [env] {}}
child {node [dummy] {}
    child {node [dummy] {child 1}
        child{node [env] {grandchild 1}}
        child{node [env] {grandchild 2}}
    }
    child {node [dummy] {child 2}
        child {node [env] {grandchild 1}}
        child {node [env] {grandchild 2}}
    }}
\end{tikzpicture}
\end{document}

结果是这样的：

也就是说，两个边（来自子节点 1 和子节点 2）与孙节点 3 相连，而孙节点 2 缺失。有人知道如何修复这个问题吗？

Answer 1

• 使用tikz你需要重新定义sibling distance
• 使用森林，你只需要确定节点之间的距离

\documentclass[tikz,
               border=3mm,
               many,
               preview
               ]{standalone}
\usepackage{forest}
\usetikzlibrary{shapes,
                trees}


\begin{document}
\begin{tikzpicture}
 [
     grow                    = right,
    level/.style = {sibling distance= 33mm/#1},
    level distance          = 6em,
    edge from parent/.style = {draw, -latex},
    every node/.style       = {font=\footnotesize},
 %
    env/.style = {circle, draw},
  dummy/.style = {draw, rounded corners,
                  top color=blue!10, bottom color=blue!60}
  ]
\node{root}
child {node [env] {}}
child {node [env] {}
    child {node [env] {child 1}
        child{node [dummy] {grandchild 1}}
        child{node [dummy] {grandchild 2}}
    }
    child {node [env] {child 2}
        child {node [dummy] {grandchild 1}}
        child {node [dummy] {grandchild 2}}
    }};
\end{tikzpicture}

\begin{forest}
for tree = {
    font = \small, 
   grow' = 0,
   l sep = 3em,
   s sep = 2ex,
if level = 3{draw, rounded corners,
             top color=blue!10, bottom color=blue!60,
             anchor=west}%
            {if level>=1{circle, draw}{s sep=12ex}},
calign=edge midpoint,
            }
[root
    [
        [child 1
            [grandchild 1]
            [grandchild 2]
        ]
        [child 2
            [grandchild 3]
            [grandchild 4]
        ]
    ]
    []
]
    \end{forest}
\end{document}