Tikz：向箭头添加标签（提供代码）

Question

以下代码生成如下所示的决策树：

我正在尝试为一些箭头添加标签，例如左下角箭头上的“x”。出于某种原因，我似乎无法在其他箭头上复制它？

\tikzset{
  treenode/.style = {align=center, inner sep=0pt, text centered,
    font=\sffamily}
}

\begin{figure}[h]
\centering
\begin{tikzpicture}[->,level/.style={sibling distance = 7cm/#1,
  level distance = 2cm}] 
\node [] {Bruises}
    child{ node [] {Gill size} 
            child{ node [] {Spore Color} 
                child{ node [] {Yes} edge from parent node[above left] {$x$}} %for a named pointer
                            child{ node [] {No}}
            }
            child{ node [] {Habitat}
                child{ node [] {Yes}}
                            child{ node [] {No}}
            }                            
    }
    child{ node [] {Texture of stalk surface below ring}
            child{ node [] {Number of rings} 
                child{ node [] {Yes}} 
                            child{ node [] {No}}
            }
            child{ node [] {Odor}
                child{ node [] {Yes}}
                            child{ node [] {No}}
            }
        }
; 
\end{tikzpicture}
\caption{An example depth 3 decision tree built on the mush dataset.}
\end{figure}

Answer 1

为了避免在使用时产生混淆edge from parent node，我认为最好的做法是给节点命名。这样，您就可以在任何节点之间以任意坐标绘制和添加路径。

这是一个例子。

\documentclass[tikz]{standalone}
\begin{document}
\tikzset{
  treenode/.style = {align=center, inner sep=0pt, text centered,
    font=\sffamily}
}
\begin{tikzpicture}[->,level/.style={sibling distance = 7cm/#1,
  level distance = 2cm}] 
\node [] {Bruises}
    child{ node [] {Gill size} 
            child{ node [] {Spore Color} 
                child{ node [] {Yes} edge from parent node[above left] {abcd}} %for a named pointer
                            child{ node [] {No}}
            }
            child{ node [] (c) {Habitat}
                child{ node [] {Yes}}
                            child{ node [] {No}}
            }                            
    }
    child{ node [] {Texture of stalk surface below ring}
            child{ node [] (a) {Number of rings} 
                child{ node [] (b) {Yes}} 
                            child{ node [] {No}}
            }
            child{ node [] {Odor}
                child{ node [] {Yes}}
                            child{ node [] {No}}
            }
        }; 
\path (a) -- (b) node[midway,above,sloped] {xyzt};
\draw[->,red] (a) -- (c) node[midway,above] {mn};
\end{tikzpicture}
\end{document}

Answer 2

我想forest为此做广告cfr 的这个回答很不错。在我看来，语法变得更加简单，添加边标签就像添加一样简单,edge label=x，当然，如果您愿意，可以添加更多箭头。

\documentclass{article}
\usepackage[edges]{forest}
\begin{document}
\begin{figure}[h]
\centering
\begin{forest}
/tikz/my edge label/.style={inner sep=5pt, midway},
for tree={edge={->},
      l sep=4em,
      s sep=3em,
      anchor=center,
      before typesetting nodes={
        if n'=1{
          edge label/.wrap value={\noexpand node [my edge label,right] {$#1$} }
        }{
          edge label/.wrap value={\noexpand node [my edge label,left] {$#1$} }
        },
      }
      }
[Bruises
 [Gill size 
  [Spore Color
   [Yes,edge label=x]
   [No,edge label=y]
  ] 
  [Habitat,alias=habitat
   [Yes] 
   [No]
  ]
 ]  
 [Texture of stalk surface below ring,alias=texture
  [Number of rings
   [Yes]
   [No]
  ] 
  [Odor
   [Yes]
   [No]
  ]
 ]
]  
\draw[red,-latex,dashed] (texture) -- (habitat) node[midway,above,sloped]{$z$};
\end{forest}
\caption{An example depth 3 decision tree built on the mush dataset.}
\end{figure}
\end{document}