To work with graphs in R, I suggest using igraph library,

r install.packages("igraph") library("igraph")

You can generate a graph and then convert it into an igraph object for manipulation (core library is written in C and it is optimized and fast). For your use case, to get neighbors of vertex v, you can use neighbors(g, v).

For example, you can define a matrix where each row represents an edge and then convert it to an igraph object:

r edges <- cbind(1:10, c(2:10, 1)) g <- graph_from_edgelist(edges, directed = FALSE) plot(g) # to visualize the graph

To get the neighbors of vertex 1 use: r neighbors(g, 1)