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I am trying to draw a graph using Graphviz, but I need to add labels on the edges. There does not seem to be any way to that in Graphviz. Are there a way out?

Stephane Rolland
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user855
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4 Answers4

295

You use the label property attached to the edge. 

digraph G {
 a -> b [ label="a to b" ];
 b -> c [ label="another label"];
}

The above generates a graph that looks something like this.

alt text

Martijn Pieters
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Andrew Walker
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    Why are the labels touching the edges? Shouldn't there be a gap? – AndreKR Jan 20 '11 at 22:27
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    @AndreKR A quick fix is to just put a space at the beginning of the label: a -> b [ label=" a to b" ]; – chembrad Jan 27 '12 at 21:30
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    This duplicates the definitions a lot. Is there a way to do something like that: `a - "a to b" > b - "b to c" > c` ? – user569825 Mar 19 '12 at 17:34
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    Another fix is to use `rankdir="LR";`, which produces a horizontal graph with labels placed above the edge without touching. – Dave Jarvis Nov 19 '12 at 23:23
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    is there a way to have the labels rotated vertically to go paralle to the line? – Justin L. Dec 08 '13 at 02:42
  • I don't believe there's any need to declare a b or c before describing edges, is there? – Russia Must Remove Putin Mar 28 '14 at 20:41
  • @Potherca Ha! Cool, I suppose, typically shouldn't edit other people's code, but in this case, probably fine. Good job, cheers! – Russia Must Remove Putin Sep 04 '14 at 14:55
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    Regarding the labels touching the edges...the work-arounds mentioned seem a little ad-hoc, and also rely on axis aligned graph edges. Labels seem often to touch the edges with complex graphs. Is there no general solution? – user2023370 Mar 07 '15 at 00:58
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    For future reference, the DOT language documentation is [here](http://www.graphviz.org/doc/info/lang.html) and the attributes documentation is [here](http://www.graphviz.org/doc/info/attrs.html). – Jens Sep 14 '16 at 00:50
  • I wish the syntax was more like `graph-easy`: https://github.com/ironcamel/Graph-Easy/wiki#hello-world – Sridhar Sarnobat Apr 05 '22 at 21:12
40

@Andrew Walker has given a great answer!

It's also worth being aware of the labeltooltip attribute. This allows an additional string to be attached to the label of an edge. This is easier for a user than the tooltip attribute, as it can be fiddly to hover directly on an edge. The syntax is as follows:

digraph G {
 a -> b [label="  a to b" labeltooltip="this is a tooltip"];
 b -> c [label="  another label" ];
}

Which gives the following result: example of a label with tooltip

Allan Bowe
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24

Landed here by googling whether labels could be on arrow's ends, for UML's composition/aggregation. The answer is yes:

"Person" -> "Hand" [headlabel="*", taillabel="1"]

enter image description here

Rudolf Real
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10

You can use label="\E" It will generate bye default label.

For Example:

digraph G {
 a -> b [ label="\E" ];
 b -> c [ label="\E"];
}
Nirav Patel
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