How to format edge labels in Graphviz?

0
votes

I created a graphviz plot to visualize a decision tree. Now I would like to add labels (e.g. True, False) to the graph on all edges.

I was using regex to manipulate the .dot file, adding the labels True and False manually. Resulting in the following file

digraph Tree {
node [shape=box, style="rounded", color="black", fontname=helvetica] ;
edge [fontname=helvetica] ;
0 [label="s5 smaller
or equal to 0.0"] ;
1 [label="bmi smaller
or equal to 0.0"] ;
0 -> 1 [labeldistance=2.5, labelangle=45, headlabel="True"] ;
3 [label="value = 110.6"] ;
1 -> 3 [headlabel="True"] ;
4 [label="value = 161.0"] ;
1 -> 4 [headlabel="False"] ;
2 [label="bmi smaller
or equal to 0.0"] ;
0 -> 2 [labeldistance=2.5, labelangle=-45, headlabel="False"] ;
5 [label="value = 174.0"] ;
2 -> 5 [headlabel="True"] ;
6 [label="value = 237.7"] ;
2 -> 6 [headlabel="False"] ;
}

This produces the following plot:

enter image description here

However, the labels don’t get nicely arranged (the arrow cuts-off the label) and I would like to format the text accordingly. Is there a way this can be done in graphviz plots? Thank you!

2
python-3.xplotgraphvizdot

2 Answers

0
votes

You can finesse label placement by adding spaces to the label text, like so:

digraph Tree {
node [shape=box, style="rounded", color="black", fontname=helvetica] ;
edge [fontname=helvetica] ;
0 [label="s5 smaller
or equal to 0.0"] ;
1 [label="bmi smaller
or equal to 0.0"] ;
0 -> 1 [labeldistance=2.5, labelangle=45, headlabel="True"] ;
3 [label="value = 110.6"] ;
1 -> 3 [headlabel="True  "] ;
4 [label="value = 161.0"] ;
1 -> 4 [headlabel="False  "] ;
2 [label="bmi smaller
or equal to 0.0"] ;
0 -> 2 [labeldistance=2.5, labelangle=-45, headlabel="False"] ;
5 [label="value = 174.0"] ;
2 -> 5 [headlabel="True  "] ;
6 [label="value = 237.7"] ;
2 -> 6 [headlabel="False    "] ;
}

Giving:
enter image description here

0
votes

[A more complete (and messy) answer]
There are multiple levels of label formatting:

  • You can insert spaces to influence X position
  • you can insert actual newlines or \n to influence Y position
  • you can use \l and \r to force left or right justification
  • you can use (pseudo) HTML strings to add more formatting combinations
  • or you can explicitly set X and Y position by setting or modifying the lp attribute of a node or edge.

see:

for explicit positioning

Examples:

digraph labels {
  a [label=a]
  b [label="b\n\n\n"]
  c [label="       c"]
  d [label="d\n\nD"]
  e [label=<<B>e</B>>]
  f
  r [label=<<table><tr><td>r</td></tr></table>>]
  s
  
  a->b [label=a123]
  b->c [label="b123\n\n\n b321"]
  c->d [label="       c123"]
  d->e [label=" d123\n\nD123"]
  e->f [label=<<I>  e123</I>>]

  r->s [label=<<table><tr><td>r123</td><td>6</td></tr><tr><td></td><td>r321</td></tr></table>>]
}

enter image description here