Question regarding circular layouts

[richardbeare]

Hi,
This is a question about whether there is a better way of doing something in ggraph than the way I came up with a few years go by hacking ggforce.

The problem is to draw brain connectivity diagrams, with brain regions laid out in a circle according to an order I specify, and the angle each region subtends setable via a mapping - basically like the "amount" aesthetic in the ggforce pie chart. The ggforce solution was a hacked combination of the arc_bar and pie chart.

I was also able to place labels radiating from the centre with

geom_text(stat="text_pie", aes(x0=0, y0=0, r0=1.1, r=1.25, amount=area, label=regionfactors,
                                     sourcenode=regionfactors, hjust=0, vjust=0), size=3)

I can get kind of close with point nodes sized according to the thing I'd like to map to angle subtended, and the edges are fine:

(Not reproducible, sorry)

this.layout.p <- ggraph::create_layout(aa, layout = "linear", circular=TRUE, sort.by = circleorder)

ggraph(graph=aa, layout = (select(this.layout.p, x, y))) + 
    geom_node_point(aes(size=area, colour=lobe)) +
    geom_edge_arc(aes(circular=TRUE)

I'd like to be able to have node label pointing outwards - (is there an appropriate angle being computed somewhere?), and also links going a bit closer to the centre, like the bezier option in ggforce.

It looks like the partition layout may be close, but requires a root node. Am I missing a more appropriate layout?

Thanks

[thomasp85]

Quite belated but can you share a plot or sketch that looks how you want it?

[richardbeare]

I found some of my old ggforce hacks, that should give you an idea - I hope this was what I was asking about.

[thomasp85]

There is no way to ensure that all edges goes to the center like in your example. Personally I also believe the behaviour you showed in the first post is much better as it avoids a lot of overplotting and is easier to read (I know biology has a thing for those arcs in the last plot but it is misguided)

as for the angle of the node label that is easier to solve since ggraph provides a helper for this:

gr <- create_notable('Meredith') %>%
  mutate(class = sample(c('Class 1', 'Class 2', 'Class 3'), n(), replace = TRUE))

ggraph(gr, 'linear', circular = TRUE) +
  geom_edge_arc(aes(alpha = after_stat(index)), strength = 0.2) + 
  geom_node_text(aes(label = class, angle = node_angle(x, y), hjust = x < 0)) + 
  coord_fixed(xlim = c(-1.2, 1.2), ylim = c(-1.2, 1.2))

As for the "arc-like" nodes this is not currently possible but I might be tempted to add this functionality to the linear layout

[thomasp85]

Ok, With the latest changes I've added a weight argument to the linear layout to get uneven spacing of the nodes, plus the layout now returns enough information so that it can be used with geom_node_arc_bar()

ggraph(gr, 'linear', circular = TRUE, weight = sample(10, gorder(gr), T)) +
  geom_edge_arc() + 
  geom_node_arc_bar(aes(r = 1.1)) + 
  coord_fixed(xlim = c(-1.2, 1.2), ylim = c(-1.2, 1.2))

I think this is as close I can get you :-)