Specify colors for each link in a force directed network, networkD3::forceNetwork()

Question

The question is to specify two different colors based on the Value or weight of the link using networkD3::forceNetwork in R. For example, Blue for the weight of links more than 1, dark for the weight of links less than 1.

Example code, copied from here (the forceNetwork section):

library(networkD3)
# Load data
data(MisLinks)
data(MisNodes)

# Plot
forceNetwork(Links = MisLinks, Nodes = MisNodes,
        Source = "source", Target = "target",
        Value = "value", NodeID = "name",
        Group = "group", opacity = 0.8)

A d3-js related question is here (I know nothing about JS so far).

Answer 1

I think you should be able to pass a javascript function wrapped in JS to linkColour to get colors based on the values in MisLinks. For example, return blue links for values > 1 and red for values <= 1.

forceNetwork(Links = MisLinks, Nodes = MisNodes,
             Source = "source", Target = "target",
             Value = "value", NodeID = "name",
             Group = "group", opacity = 0.8,
             linkColour = JS('function(l) { return l.value > 1 ? "#00F" : "#F00" }'))

Answer 2

I've just had the same problem working with networkD3.
You can do that by providing a vector depending on the values of MisLinks$value using the ifelse function:

forceNetwork(Links = MisLinks, Nodes = MisNodes,
         Source = "source", Target = "target",
         Value = "value", NodeID = "name",
         Group = "group", opacity = 0.8,
         linkColour = ifelse(MisLinks$value > 1, "blue","black"))

This solution does not depend on knowing javascript.
Hope this helps.