The strength of a vertex is the sum of the weights of the edges adjacent on that node. The strength function gives us the strength of vertices in our graph. Let's look at a small code snippet to find the degree and strength of a graph:

> degree(simple.graph)
  alice     bob charlie   david     eli 
      1       1       3       1       2 
> E(simple.graph)$weight <- c(10,20,35,15,25,35)
> strength(simple.graph)
  alice     bob charlie   david     eli 
     10      20      70      35      25 

The functions degree and strength in igraph package can be invoked to get degree and strength.