Conditional removing of vertices based on attributes in r

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!

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 :)