With default/some options, render network can be long. Here are some ways to improve the performance :

• By default, and if we don’t pass any information about coordinates, vis.js computes coordinates dynamically and wait for stabilization before rendering. You can disable or control stabilization using visPhysics :
visNetwork(nodes, edges) %>%
visPhysics(stabilization = FALSE)
• Another tips is to disabled smooth curve for edges. It’s better for performance :
visNetwork(nodes, edges) %>%
visEdges(smooth = FALSE)
• Since visNetwork_0.2.1, it’s possible to make the link between the features of package igraph and those of visNetwork. The best way to increace plotting time is actually to use igraph layout to compute coordinates before with visIgraphLayout() :
visNetwork(nodes, edges) %>%
visIgraphLayout()