How to send edges to back in tikz trees

Question

I'm using tikz trees to create the following diagram:

\begin{tikzpicture}
  [
    sibling distance        = 2em,
    level distance          = 8em,
    edge from parent/.style = {draw, -latex},
    every node/.style       = {font=\footnotesize},
    treenode/.style = {shape=rectangle, rounded corners, draw, align=center,fill=white},
    dummy/.style    = {circle,draw},
    sloped
  ]
  \node [treenode] {\textbf{Where do I have to}\\\textbf{extract data from?}}
        child[grow=right] { node [dummy] {} 
            child{ node [treenode] {Industrial control systems devices \cite{myers2018anomaly}} edge from parent}
            child{ node [treenode] {Ubiquitous computing devices \cite{yousfi2019discovering}} edge from parent}
            child{ node [treenode] {Geotags \cite{diamantini2017discovering}} edge from parent}
            child{ node [treenode] {Eye tracking devices \cite{ioannou2020mining}} edge from parent}
            child{ node [treenode] {Ventricular assist devices \cite{movahedi2019sequential}} edge from parent}
            child{ node [treenode] {WiFi-base indoor positioning systems \cite{liu2014proactive} \cite{hwang2017process}} edge from parent}
        edge from parent node [above] {Hardware}}
        child[grow=left] { node [dummy] {} 
            child{ node [treenode] {Relational databases \cite{syamsiyah2020process} \cite{andrews2020quality}} edge from parent}
            child{ node [treenode] {Electronic data interchange messages \cite{engel2016analyzing} \cite{krathu2014framework}} edge from parent}
            child{ node [treenode] {Natural language texts \cite{metsker2018identification} \cite{kabicher2011human}} edge from parent}
            child{ node [treenode] {Electronic medical records \cite{metsker2017pattern} \cite{chen2019mining}} edge from parent}
            child{ node [treenode] {Educational platforms \cite{cerezo2020process}} edge from parent}
            child{ node [treenode] {Librarian systems \cite{kouzari2018process}} edge from parent}
            child{ node [treenode] {Software development projects \cite{samalikova2011toward}} edge from parent}
            child{ node [treenode] {Different information systems \cite{myers2018anomaly} \cite{schuh2020data}} edge from parent}
        edge from parent node [above] {Software}};
\end{tikzpicture}

What can I do so that the edges are draw behind the nodes and not over them?

Welcome to TeX.SX! Please make your code compilable (if possible), or at least complete it with \documentclass{...}, the required \usepackage's, \begin{document}, and \end{document}. That may seem tedious to you, but think of the extra work it represents for TeX.SX users willing to give you a hand. Help them help you: remove that one hurdle between you and a solution to your problem. — erik, Dec 16 '20 at 18:35
Does this answer your question? How to add a node style option layer=background for node, draw...? — erik, Dec 16 '20 at 18:43
Using that answer you can add on layer=bg to your edge from parent/.style to place the edges on the background layer. — erik, Dec 16 '20 at 19:09

score 3 · Answer 1 · answered Dec 16 '20 at 19:36

Using this answer, which further refers to this one, you can tell TikZ to place something on a specific layer. Here you can add this to your edge from parent/.style definition to place the edges on a background layer called bg.

Code:

\documentclass[tikz,border=2pt]{standalone}
\pgfdeclarelayer{bg}
\pgfsetlayers{bg,main}
%%% see https://tex.stackexchange.com/a/20426
\makeatletter
\pgfkeys{%
  /tikz/on layer/.code={
    \pgfonlayer{#1}\begingroup
    \aftergroup\endpgfonlayer
    \aftergroup\endgroup
  }
}
\def\node@on@layer{\aftergroup\node@@on@layer}
\makeatother
%%%
\begin{document}
\begin{tikzpicture}
  [
    sibling distance        = 2em,
    level distance          = 9em,
    edge from parent/.style = {draw, -latex, on layer=bg},
    every node/.style       = {font=\footnotesize},
    treenode/.style = {shape=rectangle, rounded corners, draw, align=center,fill=white},
    dummy/.style    = {circle,draw},
    sloped
  ]
  \node [treenode] {\textbf{Where do I have to}\\\textbf{extract data from?}}
        child[grow=right] { node [dummy] {} 
            child{ node [treenode] {Industrial control systems devices \cite{myers2018anomaly}} edge from parent}
            child{ node [treenode] {Ubiquitous computing devices \cite{yousfi2019discovering}} edge from parent}
            child{ node [treenode] {Geotags \cite{diamantini2017discovering}} edge from parent}
            child{ node [treenode] {Eye tracking devices \cite{ioannou2020mining}} edge from parent}
            child{ node [treenode] {Ventricular assist devices \cite{movahedi2019sequential}} edge from parent}
            child{ node [treenode] {WiFi-base indoor positioning systems \cite{liu2014proactive} \cite{hwang2017process}} edge from parent}
        edge from parent node [above] {Hardware}}
        child[grow=left] { node [dummy] {} 
            child{ node [treenode] {Relational databases \cite{syamsiyah2020process} \cite{andrews2020quality}} edge from parent}
            child{ node [treenode] {Electronic data interchange messages \cite{engel2016analyzing} \cite{krathu2014framework}} edge from parent}
            child{ node [treenode] {Natural language texts \cite{metsker2018identification} \cite{kabicher2011human}} edge from parent}
            child{ node [treenode] {Electronic medical records \cite{metsker2017pattern} \cite{chen2019mining}} edge from parent}
            child{ node [treenode] {Educational platforms \cite{cerezo2020process}} edge from parent}
            child{ node [treenode] {Librarian systems \cite{kouzari2018process}} edge from parent}
            child{ node [treenode] {Software development projects \cite{samalikova2011toward}} edge from parent}
            child{ node [treenode] {Different information systems \cite{myers2018anomaly} \cite{schuh2020data}} edge from parent}
        edge from parent node [above] {Software}};
\end{tikzpicture}
\end{document}

Zarko · Accepted Answer · 2020-12-17T01:52:58.150

Alternative solutions with use of the forest package. Maybe someone will like it.

Case A: nodes have one line text (as shown in question), consequently image in portrait oriented page is a wee bit wider than page width. Therefore this solution is appropriate for landscape page:

\documentclass[margin=3.14159mm]{standalone}
\usepackage{forest}
\usetikzlibrary{arrows.meta}
\tikzset{lbl/.style = {inner sep=2pt, font=\footnotesize, midway, above}}
\begin{document}
    \begin{forest}
for tree = {
% node style
    rounded corners,
    draw,
    minimum size = 1em,
            font = \small,
% tree style
    edge = {-{Straight Barb[angle=60:2pt 3]}, semithick},
    edge path'={(!u.parent anchor) -- (.child anchor)},
    l sep=12mm,
    s sep=1mm
           }
% tree body code
[root,
    [ , circle, edge label={node[lbl] {Hard-ware}},
        %%%%    settings for the right branch
        for tree={grow=east, anchor=west, child anchor=west},
        before computing xy={l=-3,s=+22mm},
        %%%%
        [Industrial control systems devices \cite{myers2018anomaly}]
        [Ubiquitous computing devices \cite{yousfi2019discovering}]
        [Geotags \cite{diamantini2017discovering}]
        [Eye tracking devices \cite{ioannou2020mining}]
        [Ventricular assist devices \cite{movahedi2019sequential}]
        [WiFi-base indoor positioning systems \cite{liu2014proactive, hwang2017process}]
    ]
    [ , circle, edge label={node[lbl] {Soft-ware}},
        %%%%    settings for the left branch
        for tree={grow=west, anchor=east, child anchor=east},
        before computing xy={l=-3,s=-22mm},
        %%%%
        [Relational databases \cite{syamsiyah2020process} \cite{andrews2020quality}]
        [Electronic data interchange messages \cite{engel2016analyzing} \cite{krathu2014framework}]
        [Natural language texts \cite{metsker2018identification} \cite{kabicher2011human}]
        [Electronic medical records \cite{metsker2017pattern} \cite{chen2019mining}]
        [Educational platforms \cite{cerezo2020process}]
        [Librarian systems \cite{kouzari2018process}]
        [Software development projects \cite{samalikova2011toward}]
        [Different information systems \cite{myers2018anomaly} \cite{schuh2020data}]
    ]
]
\end{forest}
\end{document}

Case B: nodes have prescribed text width, consequently text in nodes is broken into more lines. With this the image can be adjust that is narrower than text width and therefore can be presented on portrait oriented page.

\documentclass[margin=3mm]{standalone}
\usepackage{forest}
\usetikzlibrary{arrows.meta}
\tikzset{lbl/.style = {inner sep=2pt, font=\footnotesize, midway, above}}
\begin{document}
    \begin{forest}
for tree = {
% node style
    rounded corners,
    draw,
    minimum size = 1em,
% prescribed nodes width and font size
        if level = 1{}{if level = 0{}{text width = 10em, /tikz/align=flush center}}{},
            font = \linespread{0.84}\selectfont,
% tree style
    edge = {-{Straight Barb[angle=60:2pt 3]}, semithick},
    edge path'={(!u.parent anchor) -- (.child anchor)},
    l sep=12mm,
    s sep=1mm
           }
% tree body code:
%  code for tree is the same as is in the above example
\end{forest}
\end{document}

How to send edges to back in tikz trees

2 Answers2