

Visualizing Directed Edges in Graphs: Don't Use Arrows - JeanPierre
http://datamining.typepad.com/data_mining/2011/04/visualizing-directed-edges-in-graphs-dont-use-arrows.html

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Emore
It's only better if you -- by reading up on convention beforehand -- know
which way an edge points; does decreasing thickness indicate an incident node,
or the opposite? Not clear on its own.

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jasondavies
Agreed; my initial interpretation was thinking of the tapered edges as comet
tails or motion blur, which is the opposite direction to what they want to
depict.

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scott_s
I also thought the thick end meant it was receiving flow as opposed to
originating it. It's also hard for me to look at the graphs and not see
motion, particularly the curved ones - years of reading comics. But reading
graphs is an expert activity, and I'm open to the idea that with practice this
method could become better.

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cdesmar
Umm... that's great for printed materials but how are you going to make that
work on a white(black)board or for that matter with a pencil?

Not sure I've done many directed graphs in print but I've done quite a few
with a marker/pencil/chalk.

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pluies_public
While I understand how arrows on the end of the edge is a bad idea, especially
if you have a lot of edges on one node; what about having arrows blended in
the edge itself?

Something like this (beware the ASCII art): o---->\----o

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6ren
I often do this in hand-drawn graphs for my own consumption, when the line is
very long (sometimes using three arrowheads): o-->\---------->\----------->o

BTW: paper mentions the problem of visual clutter of the arrowhead itself.

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steve19
I really like the gradient use on the edges. That, along with the taper,
allows a reader to easily see the direction without having to follow it till
it hits another node.

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DuckPaddle
Interesting, I feel for "trained" users who use directed graphs for work this
is a valuable technique. But even the researchers admitted it is not obvious
which way the flow goes. So I don't think it would work well for advertising
or public presentations.

The research paper makes interesting reading, and how often can you say that!

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th0ma5
I have a graph theory based application in the Android market, "Edgy," and I
doubt that I would switch to this. I think once you get used to it, it is
perhaps clearer, but I think there are many opportunities for styling and
weights that may increase clarity without having to do something that is not
expected. If this catches on, of course I'll probably go that way, but as for
now, I haven't even seen many, if any, graphs use this.

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hessenwolf
They appear to have skipped curved arrows, which would reduce the muntedness
of the graph considerably. Do please correct me if I skimmed poorly.

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thefool
I much perfer having gradients on the edges if you are going to do something
nonstandard

