How to align parent nodes to the left/top in a tree

Question

I am drawing trees in LATEX. The qtree library seems to be what I need but the parent is always placed in the center of its children like this:

    parent
    /    \ 
child_1 child_2

(I'm a new user and does not have enough reputation to post an image.)

What I want is a right-growing tree like this:

root  -- child_1  -- grandchild_1_1
      \- child_2
      \- child_3  -- grandchild_3_1
                  \- grandchild_3_2 -- great-grandchild_3_2_1
      \- child_4  -- grandchild_4_1

Rotating the qtree to right-growing is insufficient since the parent nodes are then vertically aligned to the center of their children, but I need them to remain on the top of their subtrees.

I've tried trees library of TikZ, which allows customized "growth function" to specify the position of children. However it does not consider the size of subtrees, so in this case child_4 would follow immediately under child_3, making grandchild_4_1 overlap with grandchild_3_2.

Is there a simple way to just "disable" the centering of parents in qtree? Or is there any better solution (may be writing my own macro)?

Welcome to TeX.SX! You may have a look on our starter guide. If you want, you can include your image, and remove the leading !. Then someone with enough reputation can edit it back in. — mafp, May 21 '13 at 15:05
@mafp Thanks! I think plain text is fine :) What is the leading !? — user31039, May 21 '13 at 15:14
If you include an image, the markup looks like ![description][link], there is a ! in front of it. But now you have enough rep to do it yourself anyway, and your ASCII art explains it fine, indeed. Good question, btw. — mafp, May 21 '13 at 15:18
Perhaps this is a duplicate question? Horizontal hierarchy tree in tikz-qtree: bad layout for longer node-names. And for a more complex version see: How to draw a horizontal tree with branches on the right and left?. And for another version of a genealogical tree see Joining two branches of a family tree. — Alan Munn, May 21 '13 at 15:22
@AlanMunn No it's not. I've reviewed answers to these questions and although they talked about horizontal trees it seems that none of them provide the alignment to left/top option - the parents are still center-aligned. — user31039, May 21 '13 at 16:16

score 9 · Accepted Answer · edited May 21 '13 at 21:09

I'm not sure if this is what you want, but here's a solution using the forest package. It provides an alignment parameter for aligning the children of a node which does most of what you want. I didn't know whether you wanted square edges or not, but they seem more appropriate for this kind of tree, (in the screen shot image the lines look odd, but this is an artefact of the screen rendering). I've added a simple alternative that looks a bit nicer without the squared edges.

\documentclass{article}
\usepackage{forest}
\begin{document}

\begin{forest}
grow right/.style={for tree={%
  calign=last,
  grow=east,
  ,s sep=.5cm,
  parent anchor=east,
  child anchor=west,
  edge path={\noexpand\path[\forestoption{edge}] 
     (!u.parent anchor) -- +(0pt,-10pt) |- (.child anchor)
     \forestoption{edge label};}
  }
}
,grow right
[Root [Child1 ] 
      [Child2
         [GChild1 ]
         [Gchild2 ]
         [GChild3 ]
      ] 
      [Child3
         [Gchild4 ]
         [Gchild5 ]
      ]
]
\end{forest}
\hfill
\begin{forest}
[Root,for tree={calign=last,grow=east,draw, parent anchor=east,child anchor=west} [Child1 ] 
      [Child2
         [GChild1 ]
         [Gchild2 ]
         [GChild3 ]
      ] 
      [Child3
         [Gchild4 ]
         [Gchild5 ]
      ]
]
\end{forest}
\end{document}

output of code

Edit: Notice that the children are organized in a reversed order, due to the counter-clockwise coordinates. Using the options calign=first, reversed=true in the for tree = {...} block produces the exact tree needed, as shown below:

order corrected

Thanks! It works well (quite a new package, it wasn't in my repository before updated), and I've edited your answer to correct the ordering of child nodes after reading the manual. — user31039, May 21 '13 at 21:08

score 3 · Answer 2 · edited Apr 13 '17 at 12:34

This is just a supplement to Alan Munn's answer which uses the edges library and other features of the current version of Forest. This therefore requires version 2+.

\documentclass[tikz,border=10pt,multi,rgb]{standalone}
\usepackage[edges]{forest}
\begin{document}
\begin{forest}
  for tree={
    grow'=0,
    parent anchor=children,
    child anchor=parent,
    anchor=parent,
    if n children=0{folder}{},
    edge path'={(!u.parent anchor) -- ++(5pt,0) |- (.child anchor)},
  },
  where n=1{
    calign with current edge
  }{},
  [Root
    [Child1]
    [Child2
      [GChild1]
      [Gchild2]
      [GChild3]
    ]
    [Child3
      [Gchild4 ]
      [Gchild5 ]
    ]
  ]
\end{forest}
\end{document}

This code produces the squared-edge version of the tree:

I think the small offset at the start of the path, prior to the vertical line, looks a bit neater, but this could be eliminated if preferred by changing the definition of the edge path to

edge path'={(!u.parent anchor) |- (.child anchor)},

Alternatively, deleting this line altogether results in a tree using the default path:

GChild1 and GChild4 may not be aligned if Child2 and Child3 are of different length. How to align the third level with all other 3rd level elements? — Akkumulator, Oct 15 '17 at 11:51

How to align parent nodes to the left/top in a tree

2 Answers2

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