CODEWITHSUNDEEP
rtreeigraph
user3024700
user3024700

Reputation: 51

Creating a tree graph in igraph

I am trying to create a genealogical tree in igraph (R), and I used the following code:

id = 1:5
parent = c(1,1,2,3,3)
name = c("A", "B", "C", "D", "E")
data = data.frame(id, parent, name)
n = graph.data.frame(data)
co=layout.reingold.tilford(n, flip.y=T)
plot <- plot.igraph(g,layout=co, vertex.label = name)

D and E should both have parent C, but this code often plots D and E on top of each other with only one arrow (instead of two). Does anybody have the solution for this problem?

enter image description here

Upvotes: 0

Views: 3969

Answers (2)

Anders Ellern Bilgrau
Anders Ellern Bilgrau

Reputation: 10253

First, you seem to specify the data.frame incorrectly to get your graph. The first and second column of data specify the vertices the edges run from and to, respectively. So, to get D and E as children of C, you need to have the parents in the first column. Secondly, you just specify the labels/name directly the the data.frame. I got this to work:

library("igraph")
data <- data.frame(parent = LETTERS[c(1,1,2,3,3)], id = LETTERS[1:5])
g <- graph.data.frame(data)

myformat <- function(g) {
  layout.reingold.tilford(g, root = 1, flip.y = FALSE, circular = FALSE)
}
plot(g, layout = myformat)

Imgur

Is that what you want?

Upvotes: 1

AntoniosK
AntoniosK

Reputation: 16121

I also had problems with that plotting command (not an interactive way of plotting), but I've started using tkplot (http://igraph.org/r/doc/tkplot.html) since then.

Check this version:

library(igraph)

id = 1:5
parent = c(1,1,2,3,3)
name = c("A", "B", "C", "D", "E")
data = data.frame(id, parent, name)
g = graph.data.frame(data)
tkplot(g, vertex.color="red", vertex.label=name)

You should get something like:

enter image description here

You can move the nodes (drag them), click on the arrows, change their colour (all or specific nodes), etc. Very good for visualisation. You might find some problems when you deal with very big graphs.

Just to be clear though, the problem you have in your code seems to be created by the layout command. If you just do:

library(igraph)

id = 1:5
parent = c(1,1,2,3,3)
name = c("A", "B", "C", "D", "E")
data = data.frame(id, parent, name)
g = graph.data.frame(data)
plot <- plot.igraph(g,vertex.label = name)

You should get :

enter image description here

which is exactly like tkplot, but it doesn't allow you to change the shape or other elements on the actual plot.

Upvotes: 0

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