[Tex/LaTex] Illustrating the random forest algorithm in TikZ

foresttikz-arrowstikz-pgftikz-trees

I'm trying to illustrate the workings of a random forest in TikZ by combining these two figures. The TikZ picture should have the different tree structures present in the second image while also showing the path through each tree of a single sample (red dots) as shown in the first.

This is what I have so far.

\documentclass{standalone}

\usepackage{forest}

\begin{document}
\begin{forest} for tree={l sep=3em, s sep=3em, anchor=center, inner sep=0.7em, fill=blue!50, circle, font=\Large\sffamily}
  [Training Data, draw, rectangle, rounded corners, orange, text=white
    [,red!70[[][]][,red!70[[][]][,red!70[,red!70][]]]]
    [,red!70[,red!70[[][]][,red!70]][[][[][]]]]
    [,red!70[[][]][,red!70[,red!70[][,red!70]][]]]
  ]
\end{forest}
\end{document}

I'm still struggling with:

Drawing boxes around and numbering each tree (tree 1, tree 2, tree n) as in the second image.
Getting the 3 dots between trees 2 and n.
Drawing arrows along the path that a sample takes through each tree as in image 1.
Combining the results of all trees at the bottom with the text "majority voting for classification/mean for regression"

Any help with that would be much appreciated!

Update

Thanks to user121799's awesome help, this is the finished TikZ image.

\documentclass[tikz]{standalone}

\usepackage{forest}
\usetikzlibrary{fit,positioning}

\tikzset{
  font=\Large\sffamily\bfseries,
  red arrow/.style={
    midway,red,sloped,fill, minimum height=3cm, single arrow, single arrow head extend=.5cm, single arrow head indent=.25cm,xscale=0.3,yscale=0.15,
    allow upside down
  },
  black arrow/.style 2 args={-stealth, shorten >=#1, shorten <=#2},
  black arrow/.default={1mm}{1mm},
  tree box/.style={draw, rounded corners, inner sep=1em},
  node box/.style={white, draw=black, text=black, rectangle, rounded corners},
}

\begin{document}
\begin{forest}
  for tree={l sep=3em, s sep=3em, anchor=center, inner sep=0.7em, fill=blue!50, circle, where level=2{no edge}{}}
  [
  Training Data, node box
  [sample and feature bagging, node box, alias=bagging, above=4em
  [,red!70,alias=a1[[,alias=a2][]][,red!70,edge label={node[above=1ex,red arrow]{}}[[][]][,red!70,edge label={node[above=1ex,red arrow]{}}[,red!70,edge label={node[below=1ex,red arrow]{}}][,alias=a3]]]]
  [,red!70,alias=b1[,red!70,edge label={node[below=1ex,red arrow]{}}[[,alias=b2][]][,red!70,edge label={node[above=1ex,red arrow]{}}]][[][[][,alias=b3]]]]
  [~~$\dots$~,scale=2,no edge,fill=none,yshift=-4em]
  [,red!70,alias=c1[[,alias=c2][]][,red!70,edge label={node[above=1ex,red arrow]{}}[,red!70,edge label={node[above=1ex,red arrow]{}}[,alias=c3][,red!70,edge label={node[above=1ex,red arrow]{}}]][,alias=c4]]]]
  ]
  \node[tree box, fit=(a1)(a2)(a3)](t1){};
  \node[tree box, fit=(b1)(b2)(b3)](t2){};
  \node[tree box, fit=(c1)(c2)(c3)(c4)](tn){};
  \node[below right=0.5em, inner sep=0pt] at (t1.north west) {Tree 1};
  \node[below right=0.5em, inner sep=0pt] at (t2.north west) {Tree 2};
  \node[below right=0.5em, inner sep=0pt] at (tn.north west) {Tree $n$};
  \path (t1.south west)--(tn.south east) node[midway,below=4em, node box] (mean) {mean in regression or majority vote in classification};
  \node[below=3em of mean, node box] (pred) {prediction};
  \draw[black arrow={5mm}{4mm}] (bagging) -- (t1.north);
  \draw[black arrow] (bagging) -- (t2.north);
  \draw[black arrow={5mm}{4mm}] (bagging) -- (tn.north);
  \draw[black arrow={5mm}{5mm}] (t1.south) -- (mean);
  \draw[black arrow] (t2.south) -- (mean);
  \draw[black arrow={5mm}{5mm}] (tn.south) -- (mean);
  \draw[black arrow] (mean) -- (pred);
\end{forest}
\end{document}

Best Answer

The following should do:

Use fit.
Add an appropriate node.
See here.
Add the nodes by hand.

\documentclass[tikz]{standalone}
\usetikzlibrary{fit,shapes.arrows,positioning}
\usepackage{forest}
\tikzset{marrow/.style={midway,red,sloped,fill, minimum height=3cm, single arrow, single arrow
    head extend=.5cm, single arrow head indent=.25cm,xscale=0.3,yscale=0.15,
    allow upside down}}
\begin{document}
\begin{forest} 
for tree={l sep=3em, s sep=3em, anchor=center, inner sep=0.7em, fill=blue!50,
circle, font=\Large\sffamily,where level=1{no edge}{}}
  [Training Data, draw, rectangle, rounded corners, orange, text=white,alias=TD
    [,red!70,alias=a1[[,alias=a2][]][,red!70,edge label={node[above=1ex,marrow]{}}[[][]][,red!70,edge label={node[above=1ex,marrow]{}}[,red!70,edge label={node[below=1ex,marrow]{}}][,alias=a3]]]]
    [,red!70,alias=b1[,red!70,edge label={node[below=1ex,marrow]{}}[[,alias=b2][]][,red!70,edge label={node[above=1ex,marrow]{}}]][[][[][,alias=b3]]]]
    [~$\cdots$~,scale=4,no edge,fill=none,yshift=-1em]
    [,red!70,alias=c1[[,alias=c2][]][,red!70,edge label={node[above=1ex,marrow]{}}[,red!70,edge label={node[above=1ex,marrow]{}}[,alias=c3][,red!70,edge label={node[above=1ex,marrow]{}}]][,alias=c4]]]
  ]
\node[draw,fit=(a1)(a2)(a3)](f1){};  
\node[draw,fit=(b1)(b2)(b3)](f2){};  
\node[draw,fit=(c1)(c2)(c3)(c4)](f3){};  
\path (f1.south west)--(f3.south east) node[midway,below=4em] (David) {mean};
\node[below=2em of David] (pred){prediction};
\foreach \X in {1,2,3}{\draw[-stealth] (TD) -- (f\X.north);
\draw[-stealth] (f\X.south) -- (David);}
\draw[-stealth] (David) -- (pred);
\end{forest}
\end{document}

Output

Code

\documentclass[margin=10pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning,fit}

\tikzset{
    every node/.style={draw, rectangle, align=center, text width=3cm, inner sep=0, thick, outer sep=0}
}

\begin{document}
\begin{tikzpicture}[node distance=5mm]
\node[fill=green!40, minimum height=2cm, minimum width=5cm, text width=3cm] (one) {This is\\block top left};
\node[fill=red!40,  fit={(one.west) (one.east)}, minimum height=1cm, anchor=north west, below =of one] (two) {block bottom left};
\node[fill=yellow, fit={(one)(two)},right =of two.south east, anchor=south west] (three) {This is\\block right};

\end{tikzpicture}
\end{document}

[Tex/LaTex] Extra space around nodes in forest multiline mode

This is a hack. It is provided as is. There are no guarantees. I don't even guarantee that it has anything to do with forest, multiline nodes or TeX. At this point, in case it is not clear, I should state that I guarantee nothing whatsoever. If the code dials the CIA, MI5 and the KGB and offers them your cat in exchange for a tube of Smarties, don't say I didn't warn you.

Caveat emptor...

Here's the idea:

If we put a tabular into a node in a tree which does not use align to create multiline nodes, we get just the same results as we do using align. However, tabular itself doesn't add vertical space, so we can't set that space to 0 as it is already zero.
If we put a minipage into a node in the same tree, the spacing is the same as putting the contents of the minipage in the node alone. (Assuming the node has only one line.)
So, if we could create multiline nodes as minipages rather than tabulars, then it would work as desired. (Whether what is desired is desirable is left for you to determine, gentle reader.)

This is not as straightforward as it sounds because a minipage, unlike a tabular requires a width and we don't want to have to set a width for all nodes in the tree.

Surely, there are easier ways to do this and doubtless there are far more efficient ones. Especially a TeX guru would likely do this far better.

At this point, the gentle reader is urged to review again the statement above concerning guarantees and the danger to the cats of all readers, however gentle.

We start by creating a new style squat multiline for trees of this kind:

\forestset{
  squat multiline/.style={

We need a couple of custom forest options:

    declare dimen={thiswidth}{0pt},
    declare autowrapped toks={thiscontent}{},

Now we start manipulating the nodes. We do this in cycles to ensure that each set of keys are processed for each node before the next set of keys is processed for each node.

    for tree={
      delay={

This is round one:

        thiscontent/.wrap pgfmath arg={##1}{content()},

In effect, this saves the content of the node. It copies it, basically. We delay this else the content won't be set when we try to copy it.

},

Now for the next round:

      delay+={
        content/.wrap value={\begin{tabular}{@{}c@{}}##1\\\end{tabular}},

This wraps the content in a tabular environment like that used by align=center. We are going to use this to get the width for the minipage.

        typeset node,

We typeset the node now, earlier than usual, because we need to get the width next.

},

The final round:

      before typesetting nodes={

We set thiswidth using the width of the node as it currently is.

        thiswidth/.wrap pgfmath arg={##1}{int(abs(max_x()-min_x()))},

Now we reset the content of the node in a minipage of width thiswidth. We use the copy of the contents from thiscontent because otherwise we'll get the tabular wrapper as well.

        content/.wrap pgfmath arg={\begin{minipage}[t]{\dimexpr\forestove{thiswidth}}\centering ##1\end{minipage}}{thiscontent()},

We've already got one lot of inner xsep because it was included when we typeset the node originally. So we set it to 0 to avoid getting double the usual amount:

        inner xsep=0pt,

We need to tell forest to typeset the node again:

        typeset node,
      },

Just the usual anchors from the original example:

      parent anchor=south,
      child anchor=north,
    },
  }
}

Now we can use the new style. The first example compares the default spacing with that used by squat multiline when the content of the nodes are identical:

\begin{forest}
  for tree={draw}
  [, phantom
    [A, for tree={parent anchor=south, child anchor=north}
      [B]
      [C
        [D]
        [E]
      ]
    ]
    [A, squat multiline
      [B]
      [C
        [D]
        [E]
      ]
    ]
  ]
\end{forest}

Then the example with larger nodes and a roof:

\begin{forest}
  for tree={draw},
  squat multiline
  [A,
    [B\\long node]
    [C
      [D\\long multiline, triangle]
    ]
  ]
\end{forest}

The style does not appear be responsible for the slight misalignment of the roof here as I get the same issue when I compare the default style with drawn nodes.

Comparison:

In any case, I assume that the combination of a roof and draw is unlikely to be desirable, and the misalignment is only noticeable because the nodes are drawn for purposes of illustration.

Complete code:

\documentclass[multi,tikz,border=10pt]{standalone}
\usepackage{forest}
\begin{document}
\forestset{
  squat multiline/.style={
    declare dimen={thiswidth}{0pt},
    declare autowrapped toks={thiscontent}{},
    for tree={
      delay={
        thiscontent/.wrap pgfmath arg={##1}{content()},
      },
      delay+={
        content/.wrap value={\begin{tabular}{@{}c@{}}##1\\\end{tabular}},
        typeset node,
      },
      before typesetting nodes={
        thiswidth/.wrap pgfmath arg={##1}{int(abs(max_x()-min_x()))},
        content/.wrap pgfmath arg={\begin{minipage}[t]{\dimexpr\forestove{thiswidth}}\centering ##1\end{minipage}}{thiscontent()},
        inner xsep=0pt,
        typeset node,
      },
      parent anchor=south,
      child anchor=north,
    },
  }
}
\begin{forest}
  for tree={draw}
  [, phantom
    [A, for tree={parent anchor=south, child anchor=north}
      [B]
      [C
        [D]
        [E]
      ]
    ]
    [A, squat multiline
      [B]
      [C
        [D]
        [E]
      ]
    ]
  ]
\end{forest}
\begin{forest}
  for tree={draw},
  squat multiline
  [A,
    [B\\long node]
    [C
      [D\\long multiline, triangle]
    ]
  ]
\end{forest}
\end{document}

Update

Best Answer

Related Solutions

[Tex/LaTex] Adjusting edge alignment and positioning of fitted node

Output

Code

[Tex/LaTex] Extra space around nodes in forest multiline mode

Caveat emptor...

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