Conditional removing of vertices based on attributes in r

Question

I am working with a graph that has 121 vertices and 209 edges and I am trying to remove from this graph vertices that satisfy two conditions:

1. degree(my.graph)==0
2. the name of the vertex begins with a specified character.

Here is an example showing what I want to get. From the following graph:

toy.graph <- graph.formula(121-221,121-345,121-587,345-587,221-587, 490, 588)

I want to remove vertices with degree 0 that start with 5. In this case I want to remove only vertex 588 (but not 490 and 587). I know how to remove vertices starting with 5:

delete.vertices(toy.graph,V(toy.graph)$name 
                %in% grep("^5",V(toy.graph)$name,value=T))

and how to remove vertices with degree 0:

delete.vertices(toy.graph, V(toy.graph)[degree(toy.graph)==0])

but when I try to put these two conditions together, that is

delete.vertices(toy.graph, V(toy.graph)$name %in%     
                grep("^5",V(toy.graph)$name,value=T) 
                && V(toy.graph)[degree(toy.graph)==0])

it does not work and I get back the full graph. Is there a special way of combining multiple conditions for removing vertices?

Thank you!

Familiar

Use &, not &&. (See ?Logic help page for the difference) – Pantie

I just figured it out too. I was using wrong operator for and. Thank you! – Familiar

So, when you plot it with just & instead of && you get what you want? For me, that leaves 490 in the graph, and I thought you wanted to get rid of 490 since it has a degree of 0. – Succinate

I wanted to get rid of only those nodes that satisfy both conditions, that is 490 should stay because of the name. & does exactly that. – Familiar

Answer 1

I believe this is what you want:

delete.vertices(
  toy.graph, 
  V(toy.graph)[ degree(toy.graph) == 0 & grepl("^5", V(toy.graph)$name) ] 
)

pozdrawiam :)

Nodical