Suggestion for a vignette enhancement

[fBedecarrats]

Thanks again for this great package.
One use-case I think for this package is to reproduce and enhance the DAG display proposed by daggity.net, that is node and edges with the following semiology:

I tried and found it not trivial to reproduce with {ggdag}. I think it might be useful to show how to reproduce such visualization in a vignette. Maybe it's just me, but I thought it might be of interest to other newcomers.

[krassowski]

It is not easy. I managed to get 90% there, e.g.

at which point there was almost no code left from ggdag as I had to rewrite everything using dagitty, ggforce and ggraph internals. And I did not find a way to get biasing paths 100% right (note how EDN1.9 → EDN1.10 is not coloured as biasing) as this is not exposed AFAIK as a public API of dagitty.

API-side it looks like this:

p = (
    ggplot()
    + aes(x=x, y=y, xend=xend, yend=yend)
    + geom_dagitty_edge2()
    + geom_dagitty_node()
    + geom_node_label(nudge_y=-0.3)
    + theme_dagitty()
    + scale_y_continuous(expand = expansion(mult=0.25))
    + scale_x_continuous(expand = expansion(mult=0.25))
)
(
    p %+% node_dagitty(dagitty::getExample('M-bias'))
    + p %+% node_dagitty(dagitty::getExample('mediator'))
    + p %+% node_dagitty(dagitty::getExample('Sebastiani'))
    + patchwork::plot_layout(design="AB\nCC", heights=c(1, 3), guides='collect')
    + patchwork::plot_annotation(tag_levels = 'a')
)

[fBedecarrats]

Thanks and bravo! Is there a snippet I could look at to understand how you approached this? (No hurry at all, I' m on holidays for the next 10 days)

[malcolmbarrett]

Can you all tell me your goal in replicating the dagitty site output? Do you prefer the look? Are the legends and colors helpful to you in some capacity? I definitely don't intend on being able to do @krassowski did out of box with ggdag, but there may be core components here that would be useful to add

[krassowski]

I uploaded my code here for reference https://github.com/krassowski/ggdagitty. Some places where I needed to extend ggdag include:

• support for adjusted argument in dagify (compare with here)
• wrapping ggdag::node_status to
  • add coordinates of control points to have nice curves as manually positioned in dagitty (see here)
  • add information about ancestry status for nodes, and path status for edges
• geom_dag_edges to allow bi-directional relation to be shown without curvature, see here

Some related upstream issues are:

• arrow.fill support thomasp85/ggraph#346
• Providing custom bezier control points thomasp85/ggraph#349

[malcolmbarrett]

All three of those items would be good (preferably separate) PRs to ggdag

There's already an issue for the control point problem #21