# Creating dots/lines brackets in tree with Tikz

I am asking myself if I can create dots like the ones in the picture with tikz:

Code

\begin{tikzpicture}

\tikzstyle{level 1}=[sibling distance=60mm]
\tikzstyle{level 2}=[sibling distance=33mm]
\tikzstyle{level 3}=[sibling distance=10mm]
\tikzstyle{level 4}=[sibling distance=5mm]
\node {n}
child {node {$\frac{n}{3}$}
child {node {$\frac{n}{9}$}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}}
child {node {$\frac{n}{9}$}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}}}
child {node {$\frac{n}{3}$}
child {node {$\frac{n}{9}$}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}}
child {node {$\frac{n}{9}$}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}}}
child {node {$\frac{n}{3}$}
child{node{$\frac{n}{9}$}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}}
child{node{$\frac{n}{9}$}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}
child{node {$\frac{n}{27}$}}}
};


And I want to start the dot lines at last child nodes and between the child nodes.

• Yes, you can. You can dot a line by writing \draw[dotted] .... – Alenanno Apr 29 '15 at 15:34
• Welcome to TeX SE! – cfr Apr 29 '15 at 15:52
• If you post the code you are using for the tree, somebody can show you how to do the dotted lines. (I'm not clear which ones you mean right now - the horizontal or vertical ones?) – cfr Apr 29 '15 at 15:56
• I edited the main question with the code I am using and what I especially want. – Hypertrooper Apr 29 '15 at 17:05
• This question reminds me of tex.stackexchange.com/a/120605 – Qrrbrbirlbel Apr 29 '15 at 23:16

Here is a solution using Tikz. The code was heavily based on this example of a recursion tree, but also heavily modified to fit your example image. Not sure if you wanted the cn/n to be actual fractions, but that's easily fixable starting from the code below.

## Code

\documentclass[margin=10pt]{standalone}
\usepackage{tikz}
\usepackage{tikz-qtree}
\usetikzlibrary{trees,calc,arrows.meta,positioning,decorations.pathreplacing,bending}

\tikzset{
edge from parent/.style={draw, thick, blue!70!black},
no edge from this parent/.style={
every child/.append style={
edge from parent/.style={draw=none}}},
level 3/.style={yshift=5cm},
level 4/.style={level distance=5mm}
}

\begin{document}

\begin{tikzpicture}[
level/.style={sibling distance=40mm/#1},
text=blue!70!black,
>=latex,
font=\sffamily
]

\node (z){cn}
child {node (a) {cn/2}
child {node  (b) {cn/4}
child {node (b1) {$\vdots$}[no edge from this parent]
child {node (b11) {c}}
}
child {node (b2) {$\vdots$}[no edge from this parent]
child {node (b12) {c}}
}
}
child {node (g) {cn/4}
child {node (g1) {$\vdots$}[no edge from this parent]
child {node (g11) {c}}
}
child {node (g2) {$\vdots$}[no edge from this parent]
child {node (g12) {c}}
}
}
}
child {node (d) {cn/2}
child {node  (e) {cn/4}
child {node (e1) {$\vdots$}[no edge from this parent]
child {node (e11) {c}}
}
child {node (e2) {$\vdots$}[no edge from this parent]
child {node (e12) {c}}
}
}
child {node (f) {cn/4}
child {node (f1) {$\vdots$}[no edge from this parent]
child {node (f11) {c}}
}
child {node (f2) {$\vdots$}[no edge from this parent]
child {node (f12) {c}
}
}
}
};

\node[left=5 of z]  (ln1) {cn}[no edge from this parent]
child {node (ln2) {cn}[no edge from this parent]
child {node (ln3) {cn}[no edge from this parent]
child {node (ln4) {}[no edge from this parent]
child {node (ln5) {cn}}}}};

\path (b12.north east) -- (g11.north west) node [midway] {$\cdots$};
\path (e12.north east) -- (f11.north west) node [midway] {$\cdots$};

\coordinate (cd1) at ($(f12)+(1,0)$);
\coordinate (nb1) at ($(g12)!.5!(e11)$);

\draw[blue!70!black,thick,<->,]
(cd1) -- (cd1|-z.east) node [near start, fill=white] {log(n)};

\draw[blue!70!black,dashed,thick,->]
($(z.west)+(-1em,0)$) -- (ln1);
\draw[blue!70!black,dashed,thick,->]
($(a.west)+(-1em,0)$) -- (ln2.east);
\draw[blue!70!black,dashed,thick,->]
($(b.west)+(-1em,0)$) -- (ln3);
\draw[blue!70!black,dashed,thick,->]
($(b11.west)+(-1em,0)$) -- (ln5);

\draw[blue!70!black,thick,decorate,decoration={brace,amplitude=10pt,mirror},->,-{latex[flex=1pt]}] (b11.south west) -- (f12.south east);
\end{tikzpicture}
\end{document}

• For the arrow, have you tried the arrows from arrows.meta library? (arrows is deprecated either-way.) By the way, your usage of -> and -latex is wrong (for lack of a better word). > is a short-cut and short-hand for an arrow tip that shall be used generally. Define >=latex (or >=Latex with the arrows.meta library) and then use only ->, <->, etc. – Qrrbrbirlbel Apr 29 '15 at 22:28
• @Qrrbrbirlbel Interesting. Thanks for the heads-up! I'm looking into it and fixing the code. By the way, >=latex and >=Latexseem to yield the same result, or am I missing something? – Alenanno Apr 29 '15 at 22:46
• Yes, I forgot to mention the flex and the bend options for arrows. Needs the bending library. Though, OP has used a much smaller arrow tip in relation to the curvature of the brace. – Qrrbrbirlbel Apr 29 '15 at 22:51
• @Qrrbrbirlbel Those are for rotating the arrow tip, correct? I was also interested in the various arrow tips available for arrows.meta, since I haven't found anything in the Tikz manual about this. – Alenanno Apr 29 '15 at 22:55
• (+1) just for the arrow on the curly bracket. (I thought that wouldn't work for some reason.) You might want to use font=\sffamily to match the style in the OP's image. – cfr Apr 29 '15 at 23:53

Here's a solution using forest. Note that this takes the 'like this' of the target image extremely seriously. This means that the actual specification of the main tree is very, very compact:

   [c, name=node 1
[, name=node 2 [, name=node 3 [][]][[][]]][[[][]][[][]]]
]


Obviously if you want something rather less generic, you can specify the contents of the nodes by hand.

Note also that there is really no reason for me to specify the labels of nodes 4-13 in the way I do. In particular, the specification of nodes numbered 10-13 is really just because I wanted to experiment a bit with node walks.

\documentclass[tikz,border=5pt]{standalone}
\usepackage{forest,textcomp}
\usetikzlibrary{positioning,arrows.meta,decorations.pathreplacing}
\begin{document}
\begin{forest}
for tree={
font=\sffamily,
before typesetting nodes={
if={level>0}{
if n children=0{
append/.wrap pgfmath arg={
[#1, font=\sffamily, edge=dotted]
}{content("!r")},
content={},
}{
content/.wrap 2 pgfmath args={#2n\textfractionsolidus#1}{int(level()*2)}{content("!r")}
}
}{
delay n=1{
content/.wrap value={##1n},
node walk={
every step/.style={alias=node 4}, F,
every step/.style={alias=node 10}, N,
every step/.style={alias=node 11}, N,
every step/.style={alias=node 9},
node walk={
rL,
node walk={
every step/.style={alias=node 12}, P,
every step/.style={alias=node 13}, P}
}
}
}
}
},
}
[c, name=node 1
[, name=node 2 [, name=node 3 [][]][[][]]][[[][]][[][]]]
]
\begin{scope}[font=\sffamily, >=Triangle]
\node (node 5) [left=25pt of node 4] {cn};
\foreach \i/\j in {6/3,7/2,8/1} \node (node \i) at (node 5 |- node \j) {cn};
\foreach \i/\j in {1/8,2/7,3/6,4/5} \draw [densely dashed, ->] (node \i.west) -- (node \j.east);
\path [draw, decorate, decoration={brace, amplitude=10pt}] (node 9.south east) -- (node 4.south west);
\path [draw, <->] (node 9.south east) +(15pt,0) coordinate (c) -- (c |- node 1.north) node [pos=.4, fill=white] {log(n)};
\end{scope}
\draw [dotted] (node 10.north east) -- (node 11.north west) (node 13.north east) -- (node 12.north west);
\end{forest}
\end{document}